[ARM] 3862/2: S3C2410 - add basic power management support for AML M5900 series

this patch registers the wakeup irq, sets a gpio pin to indicate the
status of system for suspend/resume operations, and adds the machine to
the supported machines for use with the simtec-pm

Signed-off-by: David Anders <danders@amltd.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>