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