[ARM] 3794/1: S3C24XX: do not defined set_irq_wake when no CONFIG_PM

Patch from Ben Dooks

Do not define set_irq_wake as a real function if
the CONFIG_PM option is not set.

Fixes bug reported by Thomas Gleixner.

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