motu: Thanks to speculation and testing by Camilo Flores, we now know that like the 828mk3 the Traveler Mark 3 also needs space in the packets for an additional two channels whenever an optical port is set to Toslink mode.

git-svn-id: http://subversion.ffado.org/ffado/trunk/libffado@2454 2be59082-3212-0410-8809-b0798e1608f0
motu: mark-3 devices equipped with optical ports which have been explicitly tested with FFADO to date have needed 2 extra audio channels in the packet formats when Toslink mode is selected on a respective optical port.  It's therefore a fair guess that perhaps this will be needed for the 896mk3 as well.  However, note that this has not been tested with an 896mk3 device yet - it is just speculation at this stage.  Suggestion and initial patch by Camilo Flores.

git-svn-id: http://subversion.ffado.org/ffado/trunk/libffado@2455 2be59082-3212-0410-8809-b0798e1608f0