mpc85xx: Use uncompressed kernel on the HiveAP-330

mpc85xx: Use uncompressed kernel on the HiveAP-330

It seems that newer builds of OpenWRT have a gzip kernel
larger than 2MB~, which for some reason fails to boot on this board.

However, we have 8MB of kernel space and currently the uncompressed
kernel is 6.5MB~, so we have some space to grow until a better
solution is worked out.

Before:
 ## Booting kernel from Legacy Image at ee840000 ...
  Image Name:   Linux-4.19.53
  Created:      2019-06-22  11:17:48 UTC
  Image Type:   PowerPC Linux Kernel Image (gzip compressed)
  Data Size:    2315724 Bytes =  2.2 MB
  Load Address: 00000000
  Entry Point:  00000000
  Verifying Checksum ... OK
 ## Loading init Ramdisk from Legacy Image at 02000000 ...
  Image Name:   OpenWrt fake ramdisk
  Created:      2019-06-22  11:17:48 UTC
  Image Type:   PowerPC Linux RAMDisk Image (uncompressed)
  Data Size:    0 Bytes =  0 kB
  Load Address: 00000000
  Entry Point:  00000000
  Verifying Checksum ... OK
 ## Flattened Device Tree blob at ec000000
  Booting using the fdt blob at 0xec000000
  Uncompressing Kernel Image ... Error: Bad gzipped data
  GUNZIP: uncompress, out-of-mem or overwrite error -
	must RESET board to recover
  Loading Ramdisk to 10000000, end 10000000 ... OK
  Loading Device Tree to 00ffa000, end 00fffc78 ... OK
  ft_fixup_l2cache: FDT_ERR_NOTFOUND

After:
 ## Booting kernel from Legacy Image at ee840000 ...
  Image Name:   POWERPC OpenWrt Linux-4.19.53
  Created:      2019-06-22  11:17:48 UTC
  Image Type:   PowerPC Linux Kernel Image (uncompressed)
  Data Size:    6724584 Bytes =  6.4 MB
  Load Address: 00000000
  Entry Point:  00000000
  Verifying Checksum ... OK
 ## Loading init Ramdisk from Legacy Image at 02000000 ...
  Image Name:   OpenWrt fake ramdisk
  Created:      2019-06-22  11:17:48 UTC
  Image Type:   PowerPC Linux RAMDisk Image (uncompressed)
  Data Size:    0 Bytes =  0 kB
  Load Address: 00000000
  Entry Point:  00000000
  Verifying Checksum ... OK
 ## Flattened Device Tree blob at ec000000
  Booting using the fdt blob at 0xec000000
  Loading Kernel Image ... OK
  OK
  Loading Ramdisk to 10000000, end 10000000 ... OK
  Loading Device Tree to 00ffa000, end 00fffc78 ... OK

Signed-off-by: Chris Blake <chrisrblake93@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com> [75 cpl limit]