disp: msm: add runtime_pm ops support in drm driver

Add runtime_pm ops support in drm driver instead
of direct sde_power_resource_enable/disable call.
It allows drm driver to use runtime pm refcount logic
to track the resources instead of custom implementation.
The change also removes the NRT_CLIENT support from
sde_power_handle code to simplify it further.

Change-Id: Ib14692dca5876703d0a230da2512d731b69b8ebb
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>