msm: mdss: fix deadlock during early wake up

Resource control lock mutex should not be held while
driver is waiting for the power work items to finish
since this can result in a deadlock.
Fix this by moving the mutex to only the area that
needs to be protected.

Change-Id: I91c440845a379a1e141178b043ad7adb33989ef2
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>