msm: mdss: ignore overflow error when sending dcs command

When horizontal line time of BLLP is too short to finish
sending dcs command packet, overflow error is reported
mistakenly. The remaining packet data will get transmitted
at next line. Therefore this overflow error can be ignored.

CRs-Fixed: 769898
Change-Id: I2239bd6bf432a1144f0f5b65bf1d82127dd4cfff
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>