Partial revert of "mpegts: add PMT monitoring option"

- removed the pmtmon option
- kept the PMT table handling for given service
Optimize the PIDs filtering

- only used CA PIDs are opened
- all PMT PIDs are opened only at the initial scan

The SAT>IP boxes have limited count of PIDs filters (and probably some
linuxdvb hardware too), so try to use these resources better.