msm_fb: display: add dcs command list for dsi command mode

DSI dcs commands and mdp pixel stream share same dsi link.
Add dcs command list to serialize sending dcs command and mdp
pixel stream to avoid contention which may cause dsi controller
to stall.

Change-Id: Ie0e687f45be479d2137eb7b56b8d32040fba2044
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>