ARM: mach-shmobile: r8a7779 PFC GPIO-only support V2

Add GPIO-only r8a7779 PFC support V2.

Only regular GPIOs are supported at this time. GPIO_FN are not
supported because they require variable bit width support in be
the shared pfc code.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>