[media] wl128x: fix build errors when GPIOLIB is not enabled

From: Randy Dunlap <rdunlap@xenotime.net>

Fix wl128x Kconfig to depend on GPIOLIB since TI_ST also
depends on GPIOLIB.

(.text+0xe6d60): undefined reference to `st_register'
(.text+0xe7016): undefined reference to `st_unregister'
(.text+0xe70ce): undefined reference to `st_unregister'

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Manjunatha Halli <manjunatha_halli@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>