mdp3: configure dma source when displaying new frame

During Linux Bootloader to kernel transition, kernel's first call
to overlay_set would reconfigure dma source configurations. This
reconfiguration could happen before vsync but the corresponding
call to overlay_commit would occur after the vsync. This race
condition could cause artifacts to appear on screen. This issue
only occurs on video mode panels.

Change-Id: I1c1274a9c32cb74276162e74c22ad35afef0eb7c
Signed-off-by: Terence Hampson <thampson@codeaurora.org>