ARM: EXYNOS: Detect power domain state on registration from DT

Initial state of power domains might vary on different boards and with
different bootloaders.

This patch adds detection of initial state of power domains when being
registered from DT.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>