ALSA: usx2y: Fix potential NULL pointer dereference

usb_alloc_urb() can fail due to kmalloc failure and push the error
upstream. Further this can cause a NULL pointer dereference in
init_pipe_urbs(). This patch avoids such a scenario.
Signed-off-by: Aditya Pakki <pakki001@umn.edu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/usx2y/usb_stream.c

@@ -104,7 +104,12 @@ static int init_urbs(struct usb_stream_kernel *sk, unsigned use_packsize,
 
 	for (u = 0; u < USB_STREAM_NURBS; ++u) {
 		sk->inurb[u] = usb_alloc_urb(sk->n_o_ps, GFP_KERNEL);
+		if (!sk->inurb[u])
+			return -ENOMEM;
+
 		sk->outurb[u] = usb_alloc_urb(sk->n_o_ps, GFP_KERNEL);
+		if (!sk->outurb[u])
+			return -ENOMEM;
 	}
 
 	if (init_pipe_urbs(sk, use_packsize, sk->inurb, indata, dev, in_pipe) ||