msm: mdss: Make sure MDP clocks are voted for while AD is stabilizing

MDP clocks were not voted for while AD stabilization was in progress,
which could result in unclocked register access in certain use cases.

Make sure MDP clocks are voted for as long as AD is stabilizing.

Change-Id: I5598beee152585a9a9bf9aefd1121f3561dbc0b8
Signed-off-by: Pravin Tamkhane <pravint@codeaurora.org>