Make Focusrite Scarlett USB audio interfaces work out of the box

[probonopd]

https://twitter.com/LundukeJournal/status/1627834277965561857 indicates that "the Scarlett USB audio board" does not work out of the box on helloSystem 0.8.0. Focusrite Scarlett audio interfaces appear to be quite popular among ambitioned podcasters, so we should ensure they work out of the box.

It is assumed that the Focusrite Scarlett Solo 3rd Gen works out of the box while other models with different numbers of channels might not, according to https://forums.freebsd.org/threads/focusrite-scarlett-6i6-1st-gen-no-sound.87676/

Following our change https://github.com/helloSystem/ISO/commit/3a6c3919ef84df5dc901f4d34144f8a8cc948111 which sets hw.usb.uaudio.default_channels=6, I'd be interested to see whether all Focusrite Scarlett USB interfaces with up to 6 channels work out of the box in the helloSystem 0.8.1 experimental builds; however I don't have hardware to test with.

Would it be a good idea to further increase hw.usb.uaudio.default_channels to support USB audio interfaces with even more channels out of the box? Why is FreeBSD not configured this way by default?