[ARM] pxa: move pxa_gpio_mode() outside of generic gpio.c

Looks like we have to live with pxa_gpio_mode() for a while, giving
its presence is actually making gpio.c not generic enough, let's
move it temporarily outside before it can be fully purged.

Signed-off-by: Eric Miao <eric.miao@marvell.com>

diff --cc arch/arm/mach-pxa/generic.c
Simple merge

diff --cc arch/arm/mach-pxa/gpio.c
Simple merge