msm: mdss: fix race conditions when enabling mdp clocks

During the early wakeup event for command mode panels
the enable of power, clocks and restore of the
controllers status happen in a different thread
context. This can cause a race condition with
multiple threads that also try to enable the power
resources and assume that the status of the
controllers has been restored.
Prevent race condition for multiple threads trying
to enable the resources, by making sure that the
complete power on, clocks and restore of the
controllers happen before return from the first
call to enable the clocks. This fixes random ping pong
timeouts observed due above described race conditions.

Change-Id: Ie3607797994a5d4f533c4d4838718b0229e32dc6
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>