disp: msm: sde: trigger pm_qos vote with irq enable

Video mode display keeps the MDP clocks in ON state but
disables irq during static screen to avoid cpu wakeup.
In such case, CPU pm_qos vote should also be removed
to allow LPM transition. This change triggers the
pm_qos vote based on mdp interrupt enable counts
instead of runtime_pm callback. It works for
multi-display concurrency also.

Change-Id: I7a60f3f593e409269e00abd7499c4a5756035615
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>