pcm/sound.* contains code that should be part of pcm/vchan.*.
Changes:
- pcm_setvchans() -> vchan_setnew()
- pcm_setmaxautovchans() -> vchan_setmaxauto()
- hw.snd.maxautovchans moved to pcm/vchan.c
- snd_maxautovchans declaration moved to pcm/vchan.h and definition to pcm/vchan.c
Sponsored by: The FreeBSD Foundation
MFC after: 1 week