[media] s5p-mfc: Only set timestamp/timecode for new frames
Timestamp i of a previously decoded buffer was overwritten for some
H.264 streams with timestamp i+1 of the next buffer. This happened when
encountering frame_type S5P_FIMV_DECODE_FRAME_SKIPPED, indicating no
new frame.
In most cases this wrong indexing might not have been noticed except
for a one frame delay in frame presentation. For H.264 streams though
that require reordering of frames for presentation, it caused a slightly
erratic presentation time lookup and consequently dropped frames in the
Pepper Flash plugin.