ARM: mach-shmobile: sh7372 A3SM support

This patch adds sh7372 A3SM power domain support.

The sh7372 A3SM hardware power domain contains the
ARM Cortex-A8 CPU Core including L2 cache. This
sleep mode can be seen as a one step deeper sleep
mode from the already existing Core Standby mode.

To wake up from A3SM sleep only a few wakeup sources
are supported - so the regular INTC controller will
not be able to help us unfortunately.

The code in this patch will enter A3SM sleep via the
regular Suspend-to-RAM interface in the case of only
wakeups supported by A3SM are enabled. If unsupported
wakeups are enabled then Core Standby will be used
instead.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>