regulator: of: Add support for parsing regulator_state for suspend state

The regulation_constraints structure includes specific field to support
suspend state for global PMIC SUSPEND/HIBERNATE mode. This patch add support
for parsing regulator_state for suspend state.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>