device layering warnings

[esmith]

df# kldload snd_ich
pcm0: <Intel ICH2 (82801BA)> port 0xe000-0xe03f,0xdc00-0xdcff irq 5 at 
device 31.5 on pci0
pcm0: <SigmaTel STAC97000/83/84 AC97 Codec>
WARNING: "dsp" (0xc969e480) is usurping "mixer"'s (0xc969fa00) cdevsw[]
df# kldunload snd_ich
dsp: cdevsw removed
dsp(30): WARNING: cdevsw removed multiple times!
dsp: cdevsw removed
pcm0: detached
sndstat: cdevsw removed
df#