ALSA: pcmtest: stop timer before buffer is released

Stop timer in the 'trigger' and 'sync_stop' callbacks since we want
the timer to be stopped before the DMA buffer is released. Otherwise,
it could trigger a kernel panic in some circumstances, for instance
when the DMA buffer is already released but the timer callback is
still running.

Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Link: https://lore.kernel.org/r/20231206223211.12761-1-ivan.orlov0322@gmail.com


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