sh: SuperH Mobile suspend support

This patch contains CONFIG_SUSPEND support to the SuperH
architecture. If enabled, SuperH Mobile processors will
register their suspend callbacks during boot.

To suspend, use "echo mem > /sys/power/state". To allow
wakeup, make sure "/sys/device/platform/../power/wakeup"
contains "enabled". Additional per-device driver patches
are most likely needed.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>