drm/msm/sde: check resource state before accessing hw

Add checking in the driver if the clocks and power resource is
enabled before accessing registers in commit path. This change is
required to make sure there is no unclocked access if power
resource enable fails.

Change-Id: I5e8aa12925e2e365e70c91bcde32e66414537f75
Signed-off-by: Abhijit Kulkarni <kabhijit@codeaurora.org>