[ALSA] usb: usbmixer error path fix

Without the patch below namelist[0] will not be freed in case
of kmalloc error.

Signed-off-by: Mariusz Kozlowski <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>
Signed-off-by: Jaroslav Kysela <[e-mail]>

sound/usb/usbmixer.c

···
 		namelist[i] = kmalloc(MAX_ITEM_NAME_LEN, GFP_KERNEL);
 		if (! namelist[i]) {
 			snd_printk(KERN_ERR "cannot malloc\n");
-			while (--i > 0)
+			while (i--)
 				kfree(namelist[i]);
 			kfree(namelist);
 			kfree(cval);