ARM: EXYNOS: Fix crash on soft reset on EXYNOS5440

The soft-reset control register is located in the XMU controller space.
Map this controller space before writing to the soft-reset controller
register.

Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Signed-off-by: Girish K S <ks.giri@samsung.com>
Signed-off-by: Kukjin <kgene.kim@samsung.com>