gpio: add MODULE_DEVICE_TABLE

The device table is required to load modules based on modaliases.

After adding MODULE_DEVICE_TABLE, below entries will be added to
modules.pcimap:

  pch_gpio             0x00008086 0x00008803 0xffffffff 0xffffffff 0x00000000 0x00000000 0x0
  ml_ioh_gpio          0x000010db 0x0000802e 0xffffffff 0xffffffff 0x00000000 0x00000000 0x0

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Cc: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>