ALSA: usb - Release capture substream URBs properly

Due to the wrong "return" in the loop, a capture substream won't be
released at disconnection properly if the device is capture only and has
no playback substream.  This caused Oops occasionally at the device
reconnection.
Reported-by: Kim Minhyoung <minhyoung.kim@lge.com>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/card.c

@@ -126,7 +126,7 @@ static void snd_usb_stream_disconnect(struct list_head *head)
 	for (idx = 0; idx < 2; idx++) {
 		subs = &as->substream[idx];
 		if (!subs->num_formats)
-			return;
+			continue;
 		snd_usb_release_substream_urbs(subs, 1);
 		subs->interface = -1;
 	}