ARM: EXYNOS4: Add MCT support for EXYNOS4412

Current MCT implementation only provide 2 event timers,
thus cannot support EXYNOS4412 which has 4 CPU cores.
This patch fixes MCT implementation to support SoCs
with 4 cores.

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