ARM: S5PC1XX: add cpu idle and system reset support

Add CPU idle support by a call to SoC build-in power management core.
Add system reset support by a simple write to system controll register.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>