sound: Improve sndstat nvlist feederchain format

[christos]

Summary

• Use snd_afmt2str() to display format conversions in feeder_format, instead of the plain hex value.
• Simplify feeder_rate contents.
• Print "ch" (e.g 2.1ch) after matrix values in feeder_matrix.
• Use snd_afmt2str() instead of a plain hex for the the rest of the feeder classes.

Sponsored by: The FreeBSD Foundation
MFC after: 2 days

[christos]

sys/dev/sound/pcm/sndstat.c

555

I think we could omit the hex here.

[dev_submerge.ch]

sys/dev/sound/pcm/sndstat.c

555

I suppose we can use snd_afmt2str() as in feeder_format, otherwise it looks a bit strange in the feeder chain.

[christos]

Use snd_aftm2str() instead of plain hex value for the rest of the feeder
classes.

[christos]

Bump.