avformat/utils: estimate_timings_from_pts - increase retry counter, fixes...

avformat/utils: estimate_timings_from_pts - increase retry counter, fixes invalid duration for ts files with hevc codec

Fixes a mpegts file with hevc that fails estimating duration. Increasing number of
retries fixes the issue.

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>