ALSA: ctxfi - Fix deadlock with xfi-timer

The PCM x-fi native update routine can cause deadlocks when the
trigger(START) is called while the stream is running.

This patch fixes the deadlock by just postponing the pcm period update
to the next possible wake-up.  Also it adds the flip of ti->running
flag (just to be sure as now).

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