Add a function to set the SCU low-power mode for SMP CPUs. This
centralizes this functionality rather than having to expose the
SCU register definitions to each platform.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
The SCU can be used by non-realview platforms, so make it visible
for other people to use rather than having them copy the header file.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>