mdss: display: queue dcs commands at video active period

Since dcs command is transmitted at BLLP by dsi controller for
video mode panel, dcs commands need to be queued to hardware
during video active period so that they can be transmitted at
next BLLP.

CRs-fixed: 525685
Change-Id: I90a28b7178bd21fd4c71903937809154380227e7
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>