dvbapi: Fix handling demux stop PMT commands

The 9F 80 3F 04 (stop decoding on demux) PMT messages was unhandled.
Problem since r9869, exposed by r9889.


git-svn-id: http://streamboard.de.vu/svn/oscam/trunk@9914 4b0bc96b-bc66-0410-9d44-ebda105a78c1