When you attempt to kldload snd_sb16 and then unload it, the system crashes.

When you attempt to kldload snd_sb16 and then unload it, the system crashes.

the problem turns out to be in snd_pcm.  snd_sbc needs a dependancy on
snd_pcm.  Without it, if you load a module that depends on both snd_sbc and
snd_pcm (like snd_sb16), then later try to unload it, the system may
unload snd_pcm before snd_sbc causing a panic.

Reported-by: Galen Sampson <galen_sampson@yahoo.com>, esmith <esmith@patmedia.net>