dsp_open: rearrange to only hold one lock at a time
dsp_close: ditto
mixer_hwvol_init: delete locking, the only consumer seems to
be the ess driver and it only call it a creation time, I
think the device will be stable across the sleepable malloc.
cmi interrupt routine: Release locks while caller chn_intr,
either this or do what emu10k1 does which is have no locks
at in the interrupt handler.
Submitted by: mat@cnd.mcgill.ca
42c3555cff