ALSA: snd-usb: Fix uninitialized variable usage

Purely cosmetic, but fixes the following build warning.

  CC [M]  sound/usb/quirks.o
sound/usb/quirks.c: In function ‘snd_usb_apply_boot_quirk’:
sound/usb/quirks.c:429:6: warning: ‘err’ may be used uninitialized in this function [-Wuninitialized]
Signed-off-by: NDaniel Mack <zonque@gmail.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/usb/quirks.c

@@ -426,7 +426,7 @@ static int snd_usb_cm106_boot_quirk(struct usb_device *dev)
  */
 static int snd_usb_cm6206_boot_quirk(struct usb_device *dev)
 {
-	int err, reg;
+	int err  = 0, reg;
 	int val[] = {0x2004, 0x3000, 0xf800, 0x143f, 0x0000, 0x3000};
 
 	for (reg = 0; reg < ARRAY_SIZE(val); reg++) {