Currently the min/max sample rate reported for a given VCHAN is whatever
is specified in dev.pcm.X.[play|rec].vchanrate, and is the same for both
the min and the max. For example, if *.vchanrate is set to 48000, then
the min/max will be both 48000. Fix this by assigning the min/max to
either the physical channel's min/max, or, when hw.snd.feeder_rate_round
is set to 0, to feeder_rate_[min|max].
Sponsored by: The FreeBSD Foundation
MFC after: 2 days