ARM: mach-shmobile: sh7372 A3SP support (v4)

This change adds support for the sh7372 A3SP power domain.

The sh7372 A3SP hardware power domain contains a
wide range of I/O devices. The list of I/O devices
include SCIF serial ports, DMA Engine hardware,
SD and MMC controller hardware, USB controllers
and I2C master controllers.

This patch adds the A3SP low level code which
powers the hardware power domain on and off. It
also ties in platform devices to the pm domain
support code.

It is worth noting that the serial console is
hooked up to SCIFA0 on most sh7372 boards, and
the SCIFA0 port is included in the A3SP hardware
power domain. For this reason we cannot output
debug messages from the low level power control
code in the case of A3SP.

QoS support is needed in drivers before we can
enable the A3SP power control on the fly.

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