Seperate the IRQ power management code out of
the pm.c file, and add it to the relevant
system class devices.

Also make the suspend and resume code take
notice of the fact these registers can be
moved by compile time code.

Add fix from Ilya Yanok to also save the
INTSUBMSK over sleep.
Signed-off-by: NBen Dooks <ben-linux@fluff.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>