According to the alsa-info.txt in the pipewire issues of #747 and #1206,
the Front Playback Volume is shared by Headphone and Lineout or
Headphone and Speaker, But Headphone, Lineout or Speaker they all have
independent Playback Switch, change to only use switch to mute the
Lineout or Speaker. This could resolve the issues of #747 and #1206.
See #1206 and #747
Motu M4 has four inputs (two line-in inputs, and two complete ones
with gain and XLR and whatnot), as well as four outputs (two monitor
pairs, and an unnaccounted headphone).
Sadly, like a few other interfaces, it wasn't being given an input
profile, since the matching code goes through default.conf testing
each config, and ends up selecting 'analog-surround-40', which does
not have input mapping. The inputs would fallback to 'multichannel-
input', which also doesn't have input paths.
Add input paths to all analog-surround-* mappings, and remove their
'direction=output' fields since they handle both out and in.
