msm_fb: display: Fix blend configuration for command mode panels

For command mode panels, blend registers does not get configured
as per the use case. This leads to incorrect blending of layers
resulting in lower layers (eg. wallpaper or buttons in video
playback) to show above the upper ones, making overall user
experience to go bad. In order to resolve the issue, blend registers
are now configured properly by as per the use case.

CRs-Fixed: 410029
CRs-Fixed: 415553
Change-Id: Ibe7d594e0ad6a6f4d75ed2e59c7382c09b65d624
Signed-off-by: Mayank Chopra <makchopra@codeaurora.org>