drm/sde: use power handle api to vote for core clock

Update SDE driver to use the power handle API for
voting the core clock and regulator. This change
also cleans up bunch of error paths in sde_kms init.

Conflicts:
	drivers/gpu/drm/msm/msm_drv.c
	drivers/gpu/drm/msm/msm_drv.h
Change-Id: I0acdd2308f7e19053d5ec0a8ae148ee6e4bc2433
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>
[narendram@codeaurora.org: Resolve conflict in
msm_drv.c and  msm_drv.h]
Signed-off-by: Narendra Muppalla <narendram@codeaurora.org>