ARM: mach-shmobile: R-Mobile A1 support.

This adds preliminary support for the R8A7740 (R-Mobile A1) CPU

Timer, serial, gic, clock are supported at this point.
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>