[media] rtl28xxu: fix return value check in rtl2832u_tuner_attach()

In case of error, the function platform_device_register_data() returns
ERR_PTR() and never returns NULL. The NULL test in the return value check
should be replaced with IS_ERR().
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/usb/dvb-usb-v2/rtl28xxu.c

@@ -1293,7 +1293,7 @@ static int rtl2832u_tuner_attach(struct dvb_usb_adapter *adap)
 						     "rtl2832_sdr",
 						     PLATFORM_DEVID_AUTO,
 						     &pdata, sizeof(pdata));
-		if (pdev == NULL || pdev->dev.driver == NULL)
+		if (IS_ERR(pdev) || pdev->dev.driver == NULL)
 			break;
 		dev->platform_device_sdr = pdev;
 		break;