msm: mdss: ignore overflow error when trigger BTA for video mode panel

This overflow only happens once after device is out of phy reset state
when BTA is triggered, however, data are still transmitted and BTA
interrupt still returns, indicating that there is nothing wrong with
data and panel. After the first overflow is ignored, there is no such
error any more when s/w trigger more BTAs.

Change-Id: Icb861e2232bda22f8fde008cf8e439594aef6732
Signed-off-by: Huaibin Yang <huaibiny@codeaurora.org>