msm: mdss: do not print error in case sync_trigger is enabled

In case sync trigger is enabled, then DCS commands are only
sent for both the DSI controller when transfer call for the
second DSI controller happens. So in that case do not print
error log for the first controller if DCS command is not sent.

Change-Id: I5c302f55f15735970cd5f6c8d0b31c55b447433f
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>