USB-Audio: add Steinberg UR44C profile

USB-Audio: add Steinberg UR44C profile

The UR44C exposes six playback and eight capture channels, while the
UR44 UCM profile defines only four playback and six capture channels.
This causes PipeWire and WirePlumber to reject the UCM profile.

Add a dedicated UR44C profile with split PCMs for its DAW Mix 1,
DAW Mix 2, and FX Bus playback pairs, plus its six direct and two
streaming capture channels.

Closes: https://github.com/alsa-project/alsa-ucm-conf/pull/835
Fixes: https://github.com/alsa-project/alsa-ucm-conf/issues/799
Signed-off-by: Polyvox <obsidianzero@gmail.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>