ARM: mach-shmobile: r8a7740: add PFC support.

This adds PFC support for the R8A7740 (R-Mobile A1) CPU
This patch is based on v0.1 manual

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>