ARM: EXYNOS: Add MCPM call-back functions

Add machine-dependent MCPM call-backs for Exynos5420. These are used
to power up/down the secondary CPUs during boot, shutdown, s2r and
switching.

Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Signed-off-by: Inderpal Singh <inderpal.s@samsung.com>
Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Reviewed-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>