HACK: drm/msm/mdp5: Make sure mdp5 clocks aren't disbaled when we need them

mdp5_hw_init configures registers but may not have clocks enabled. Add
calls to enable/disable clocks in this func.

Comment out a mdp5_disable() call in mdp5_kms_init. For now, this makes
sure we have clocks all the time. This will be removed when runtime
pm is added, and we identify all paths where we risk clocks being
disabled when they shouldn't.

Signed-off-by: Archit Taneja <architt@codeaurora.org>