avformat/mov: Increment stsd_count while processing stsd data; avoids leaks.

In the event of ff_mov_read_stsd_entries() failure, sc->stsd_count
is not updated, even if the function allocates extradata memory.
Instead update the sc->stsd_count as entries are parsed so that
mov_read_close() can do the right thing.

Signed-off-by: Dale Curtis <dalecurtis@chromium.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
