motu: the original 828 does not have MIDI I/O, so don't create MIDI ports for it...

motu: the original 828 does not have MIDI I/O, so don't create MIDI ports for it.  This allows audio to be passed to analog-1 on playback since the respective bytes in the packet are no longer being zeroed by encodeSilencePortToMotuMidiEvents() in the case where the MIDI ports were not in use.  Previously, with disabled (unused) MIDI ports processWriteBlock() would call encodeSilencePortToMotuMidiEvents() via encodeSilencePortToMotuEvents().  There is still no audio output in general though: this patch just fixes an anomally noticed in the packets while searching for a reason behind the missing audio output.

git-svn-id: svn+ssh://ffado.org/ffado/trunk@2353 2be59082-3212-0410-8809-b0798e1608f0