ARM: mach-shmobile: sh7372 Core Standby Suspend-to-RAM

Add sh7372 Core Standby sleep mode support and tie it
in with the shared SH-Mobile ARM suspend code.

The Core Standby mode is the lightest sh7372-specific
sleep mode, cutting power to the ARM core excluding the
L2 cache. Any interrupt source can be used for wakeups.

The low level portion of this code is based on the
TI OMAP sleep code in sleep34xx.S, thanks to them.

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