mpegtsparse: don't free PAT structure which may still be needed later

mpegtsparse: don't free PAT structure which may still be needed later

This is a problem if you tune to a channel which uses pid X and later tune to
another channel where X is used for another table (e.g. PMT).

The code that does that was actually already there but never used because the
pat structure was freed before. The commit that introduced those lines intended
to fix a memory leak, but we clean things up elsewhere.

Fixes #622725.