mdss: display: turn on mdp clocks after acquiring dsi lock

At command mode panel, mdp related clocks are turned on/off
frequently to save power.  It will be turned off after 4
vsync time if no kickoff happen.
MDSS_EVENT_DSI_CMDLIST_KOFF event will try to acquire lock
of dsi controller and it may take some times to complete it.
Therefore mdp clocks have to be turned on after acquire lock
of dsi controller instead of before.

Change-Id: Ied3de9f96fabbc06b43cad23ac54659c785012d3
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>