"idx" is controled by the user and can be a negative offset into the
input_names[] array.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

(cherry picked from commit bd5fe738)
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>