ALSA: control - off by one in store_mode()

If count is 16 then this will put the NUL terminator one element beyond
the end of the array.

Fixes: cb17fe0 ("ALSA: control - add sysfs support to the LED trigger module")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/YGcDOtrimR46vr0k@mwanda
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/control_led.c

@@ -391,7 +391,7 @@ static ssize_t store_mode(struct device *dev, struct device_attribute *attr,
 {
 	struct snd_ctl_led *led = container_of(dev, struct snd_ctl_led, dev);
 	char _buf[16];
-	size_t l = min(count, sizeof(_buf) - 1) + 1;
+	size_t l = min(count, sizeof(_buf) - 1);
 	enum snd_ctl_led_mode mode;
 
 	memcpy(_buf, buf, l);