ALSA: mixart: Add sanity check for timer notify streams

The miXart timer notification is a variable length, and if a hardware
is screwed up, we may access over the actual data size.  Let's add a
sanity check and bail out if an invalid value is received.

Link: https://lore.kernel.org/r/20211207153323.27098-1-tiwai@suse.de


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