dvb: downgrade error messages
dvb: downgrade error messages

The old DVB plugin generate syntax error messages on valid MRLs that
the normal DTV plugin just fails to open (e.g. due to missing tuner).
This has proven very confusing.

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc