ARM: S3C24XX: fix building without PM_SLEEP

We get lots of link errors based on the assumption that
any s3c24xx kernel would enable CONFIG_PM_SLEEP if it
enables CONFIG_PM. This tries to clean that up.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kukjin Kim <kgene@kernel.org>