[ARM] 4730/1: S3C2412: Ensure the PWRCFG has the right mode for RTC wake

Ensure that if the RTC IRQ is not selected for wake in the
base configuration, then the PWRCFG has the same value set
in it.

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