ARM: mach-shmobile: Use pullups for AG5EVM KEYSC pins

Follow up to pfc-sh73a0.c's pull-up support.
Change GPIO_FN_KEYINx to GPIO_FN_KEYINx_PU.

Signed-off-by: Takashi YOSHII <takashi.yoshii.zj@renesas.com>
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>