media: dvb: mpq: Fix notification of first video PTS

demux reported the first video PTS using the PTS value within the
first video PES after playback starts. When playbak starts demux
drops all PES data until reaching sequence-header, the PTS of the
first PES holding a video frame after reaching the sequence header
should be used and not the one in the first PES before data is dropped.

Change-Id: I4c2b3f79e8320239d7c8e165093d4c6111dc8a27
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>
Signed-off-by: Neha Pandey <nehap@codeaurora.org>