drm/msm: DT support for 8960/8064 (v3)

Now that we (almost) have enough dependencies in place (MMCC, RPM, etc),
add necessary DT support so that we can use drm/msm on upstream kernel.

v2: update for review comments
v3: rebase on component helper changes

Signed-off-by: Rob Clark <robdclark@gmail.com>