ARM: EXYNOS4: Add support MCT PPI for EXYNOS4212

This patch implements clock event timer using MCT PPI
and make EXYNOS4212 use MCT PPI instead of MCT SPI.

Signed-off-by: Changhwan Youn <chaos.youn@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>