ARM: S5P6440: Add Clock and PLL support

This patch adds clock and pll support for S5P6440. This patch are based on
Harald Welte's patches and Ben's plat-samsung.

Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>