viafb: fix rmmod bug

viafb: fix rmmod bug

This fixes a bug caused by changing pointers (viafb_mode, viafb_mode1)
assigned by module_param.  It reduces driver complexity by not needlessly
changing these vars as they are only read once and removing now
superfluous code.

On unpatched kernels loading viafb with viafb_mode or viafb_mode1 option
used and afterwards unloading it results in:

kernel BUG at mm/slub.c:2926!
invalid opcode: 0000 [#1] PREEMPT
last sysfs file: /sys/devices/virtual/block/loop0/removable
Modules linked in: snd_hda_codec_realtek snd_hda_intel snd_hda_codec
snd_hwdep snd_pcm rtl8187 snd_timer eeprom_93cx6 mmc_block snd soundcore
via_sdmmc fb snd_page_alloc i2c_algo_bit i2c_viapro ehci_hcd uhci_hcd
cfbcopyarea mmc_core cfbimgblt cfbfillrect video output [last unloaded:
viafb]

  Pid: 3355, comm: rmmod Not tainted (2.6.31-rc1 #0)
  EIP: 0060:[<c106a759>] EFLAGS: 00010246 CPU: 0
  EIP is at kfree+0x80/0xda
  EAX: c17c2da0 EBX: dc7edbdc ECX: 0000010f EDX: 00000000
  ESI: c102c700 EDI: dc7ed8fa EBP: d703ff2c ESP: d703ff20
   DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
  Process rmmod (pid: 3355, ti=d703e000 task=db1412c0 task.ti=d703e000)
  Stack:
   dc7edbdc 00000014 00000016 d703ff40 c102c700 dc7f45d4 dc7f45d4 00000880
   d703ff4c c103e571 00000000 d703ffac c103e751 66616976 da140062 db89ba80
   00000328 d702edf8 db89ba80 d703ff9c c105d0f0 00000200 da14f898 00000014
  Call Trace:
   [<c102c700>] ? destroy_params+0x1e/0x2b
   [<c103e571>] ? free_module+0xa2/0xd7
   [<c103e751>] ? sys_delete_module+0x1ab/0x1da
   [<c105d0f0>] ? do_munmap+0x20a/0x225
   [<c10029b4>] ? sysenter_do_call+0x12/0x26
  Code: 10 76 7a 8d 87 00 00 00 40 c1 e8 0c c1 e0 05 03 05 1c 87 41 c1 66 83 38 00 79 03 8b 40 0c 8b 10 84 d2 78 12 66 f7 c2 00 c0 75 04 <0f> 0b eb fe e8 6f 5a fe ff eb 47 8b 55 04 8b 58 0c 9c 5e fa 3b
  EIP: [<c106a759>] kfree+0x80/0xda SS:ESP 0068:d703ff20

This is caused by the current code changing the pointers assigned by
module_param.  During unload it tries to free the memory the pointers
point at which is now part of an internal structure.

The patch simply avoids changing the pointers.  This is okay as they are
read only once during the initialization process.

Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: Scott Fang <ScottFang@viatech.com.cn>
Cc: Joseph Chan <JosephChan@via.com.tw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>