Revert "msm_fb: display: extend mutex protection for mdp pan display"

This reverts commit 8d28053ba306ad5d95f63adfd0f9349fb9da4306.

Change-Id: Iea53ac96f2c7fe993d9d025742db217dfdacb480
mdp: dtv: Fix pipe staging, again

Change-Id: I3ad7483368a99674504e4d0d24a17865b0219b50