MFC:
MFC:

Limit total hardware playback channels to just 1. The reliability of
it's multi DAC / playback channels is not that good. Enabling vchans
make the bug more visible since playback allocation will look for
possible free hardware channels first (i.e: the next DAC, the very first
has been consumed by vchan mixer) which in this case has been proven faulty.

Tested by:	Dominic Fandrey <LoN_Kamikaze at gmx dot de>
URL:		http://lists.freebsd.org/pipermail/freebsd-stable/2007-December/039022.html
Approved by:	re (kensmith)

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