ALSA: usb-audio: harmless underflow in snd_audigy2nx_led_put()

We want to verify that "value" is either zero or one, so we test if it
is greater than one.  Unfortunately, this is a signed int so it could
also be negative.  I think this is harmless but it introduces a static
checker warning.  Let's make "value" unsigned.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>