ALSA: snd_rtctimer: handle RTC interrupts with a tasklet

The calls to rtc_control() from inside the interrupt handler can
deadlock the RTC code, so move our interrupt handling code to a tasklet.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Acked-By: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>