ALSA: control: potential uninitialized return value

      Smatch complains that "ret" might be uninitialized.

Fixes: fbd3eb7f66c5 ("ALSA: control: Add verification for kctl accesses")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200108053706.h3hcnvmnf62wkjac@kili.mountain
Signed-off-by: Takashi Iwai <tiwai@suse.de>