ALSA: vx: Use nonatomic PCM ops

Rewrite VXpocket and VX222 drivers to use the new PCM nonatomic ops.
The former irq tasklet is replaced with a threaded irq handler, and
the tasklet for the PCM delayed start is simply merged into the normal
PCM trigger, as well as the replacement of spinlock with mutex.

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