media: dvb-usb: fix uninit-value in vp702x_read_mac_addr

If vp702x_usb_in_op fails, the mac address is not initialized.
And vp702x_read_mac_addr does not handle this failure, which leads to
the uninit-value in dvb_usb_adapter_dvb_init.

Fix this by handling the failure of vp702x_usb_in_op.

Fixes: 786baecf ("[media] dvb-usb: move it to drivers/media/usb/dvb-usb")
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/usb/dvb-usb/vp702x.c

@@ -291,16 +291,22 @@ static int vp702x_rc_query(struct dvb_usb_device *d, u32 *event, int *state)
 static int vp702x_read_mac_addr(struct dvb_usb_device *d,u8 mac[6])
 {
 	u8 i, *buf;
+	int ret;
 	struct vp702x_device_state *st = d->priv;
 
 	mutex_lock(&st->buf_mutex);
 	buf = st->buf;
-	for (i = 6; i < 12; i++)
-		vp702x_usb_in_op(d, READ_EEPROM_REQ, i, 1, &buf[i - 6], 1);
+	for (i = 6; i < 12; i++) {
+		ret = vp702x_usb_in_op(d, READ_EEPROM_REQ, i, 1,
+				       &buf[i - 6], 1);
+		if (ret < 0)
+			goto err;
+	}
 
 	memcpy(mac, buf, 6);
+err:
 	mutex_unlock(&st->buf_mutex);
-	return 0;
+	return ret;
 }
 
 static int vp702x_frontend_attach(struct dvb_usb_adapter *adap)