Revert "Revert "msm_fb: display: remove background invert alpha option for alpha drop pipe""

  * This is working with the latest display driver changes. No more
    flicker during transitions.

This reverts commit 69a761dbaadee12ae802e993288b4d899da5110b.

Change-Id: I070c408040fffc1fbd22d51bc61a46e0082a457c