S5P: SYSMMU: Remove System MMU device driver

This patch removes System MMU device driver from arm/plat-s5p tree
for transition to implement IOMMU driver.
Although controlling System MMU in this removing driver
is similar to the new IOMMU driver in the following patch,
the new one is almost rewrite of this driver and there is no
benefit to moving the driver file from arch/arm/ to drivers/iommu.

Signed-off-by: KyongHo Cho <pullip.cho@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>