ALSA: pcxhr: Use nonatomic PCM ops

This time PCXHR, another Digigram boards: like the previous patches,
the conversion is straightforward, replacing spinlocks with mutexes,
merging the irq tasklet into the threaded irq handler and the PCM
trigger tasklet back to the trigger callback.

Signed-off-by: Takashi Iwai <tiwai@suse.de>