disk: part_efi: fix check of the max partition size

disk: part_efi: fix check of the max partition size

the last value acceptable value for offset is last_usable_lba + 1
and not last_usable_lba - 1

issue found with SDCARD partition commands on u-boot 2015.10
but this part of code don't change

1- create GPT partion on all the card
  > gpt write mmc 0 name=test,start=0,size=0
  > part list mmc 0

Partition Map for MMC device 0  --   Partition Type: EFI

Part      Start LBA          End LBA                       Name
            Attributes
            Type GUID
            Partition GUID
  1        0x00000022       0x003a9fde       "test"
            attrs:     0x0000000000000000
            type:     ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
            type:     data
            guid:     b710eb04-45b9-e94a-8d0b-21458d596f54

=> Start = 0x22*512 = 0x4400
=> Size = (0x003a9fde-0x22+1) * 512  = 0x753F7A00

2- try to recreate the same partition with the next command
   (block size:512 bytes = 0x200)

  > gpt write mmc 0 name=test,start=0x4400,size=0x753F7A00
    Writing GPT: Partitions layout exceds disk size

  > gpt write mmc 0 name=test,start=0x4400,size=0x753F7800
    Writing GPT: Partitions layout exceds disk size

  > gpt write mmc 0 name=test,start=0x4400,size=0x753F7600
    Writing GPT: success!

Partition Map for MMC device 0  --   Partition Type: EFI

Part      Start LBA          End LBA                       Name
            Attributes
            Type GUID
            Partition GUID
  1        0x00000022       0x003a9fdc       "test"
            attrs:     0x0000000000000000
            type:     ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
            type:     data
            guid:     36ec30ef-7ca4-cd48-97cd-ea9fb95185d0

the max LBA when the size is indicated (0x003a9fdc) is lower than
when u-boot compute the max allowed value with size=0 (0x003a9fde)

in the code :

     /* partition ending lba */
     if ((i == parts - 1) && (partitions[i].size == 0))
		/* extend the last partition to maximuim */
		gpt_e[i].ending_lba = gpt_h->last_usable_lba;
     else
		gpt_e[i].ending_lba = cpu_to_le64(offset - 1);

so offset = gpt_h->last_usable_lba + 1 is acceptable !
but the test (offset >= last_usable_lba) cause the error

END

Signed-off-by: Patrick Delaunay <patrick.delaunay73@gmail.com>disk: part_efi: fix check of the max partition size
the last value acceptable value for offset is (last_usable_lba + 1)
and not (last_usable_lba - 1)

issue found with SDCARD partition commands on u-boot 2015.10
but this part of code don't change

1- I create GPT partion on all the card (start and size undefined)

  > gpt write mmc 0 name=test,start=0,size=0
  > part list mmc 0

Partition Map for MMC device 0  --   Partition Type: EFI

Part      Start LBA          End LBA                       Name
            Attributes
            Type GUID
            Partition GUID
  1        0x00000022       0x003a9fde       "test"
            attrs:     0x0000000000000000
            type:     ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
            type:     data
            guid:     b710eb04-45b9-e94a-8d0b-21458d596f54

=> Start = 0x22*512 = 0x4400
=> Size = (0x003a9fde-0x22+1) * 512  = 0x753F7A00

2- I try to recreate the same partition with the command gpt write
   and with start and size values (block size:512 bytes = 0x200)

  > gpt write mmc 0 name=test,start=0x4400,size=0x753F7A00
    Writing GPT: Partitions layout exceds disk size

  > gpt write mmc 0 name=test,start=0x4400,size=0x753F7800
    Writing GPT: Partitions layout exceds disk size

  > gpt write mmc 0 name=test,start=0x4400,size=0x753F7600
    Writing GPT: success!

  I check the partition created :

  > part list mmc 0

Partition Map for MMC device 0  --   Partition Type: EFI

Part      Start LBA          End LBA                       Name
            Attributes
            Type GUID
            Partition GUID
  1        0x00000022       0x003a9fdc       "test"
            attrs:     0x0000000000000000
            type:     ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
            type:     data
            guid:     36ec30ef-7ca4-cd48-97cd-ea9fb95185d0

=> but the max LBA when the size is indicated (0x003a9fdc) is lower than
   when u-boot compute the max allowed value with size=0 (0x003a9fde)

3- in the code, just after my patch, line 446

     /* partition ending lba */
     if ((i == parts - 1) && (partitions[i].size == 0))
		/* extend the last partition to maximuim */
		gpt_e[i].ending_lba = gpt_h->last_usable_lba;
     else
		gpt_e[i].ending_lba = cpu_to_le64(offset - 1);

  so offset = gpt_h->last_usable_lba + 1 is acceptable !
  (it the value used when size is 0)

  but today the test (offset >= last_usable_lba) cause the error
  my patch only solve this issue

END

Signed-off-by: Patrick Delaunay <patrick.delaunay73@gmail.com>