Don't grab audio_lock in filt_midi{read,write} if NOTE_SUBMIT is set.

Don't grab audio_lock in filt_midi{read,write} if NOTE_SUBMIT is set.

Fixes panics caused by attempts to grab audio_lock twice in the
interrupt code path: once in the low-lever interrupt handler and once
in selwakeup()

This is exactly how audio(4) handles this problem.

ok mpi