ALSA: pcsp - Fix starting the stream with HRTIMER_CB_IRQSAFE_UNLOCK

With the callback mode HRTIMER_CB_IRQSAFE_UNLOCK, the start of the
stream with zero delay doesn't work.  Since IRQSAFE mode is removed,
we have to change the pcsp start-up code.

This patch splits the callback function to two parts, the triggering
of the port and the calculation of the expire time, and the update of
the ALSA PCM core.  The first part is called both from the trigger-start
and the hrtimer callback while the latter is handled only in the
hrtimer callback.

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