media: i2c: ds90ub960: fix error handling in ub960_rxport_add_serializer()

Smatch warns:
 drivers/media/i2c/ds90ub960.c:1671 ub960_rxport_add_serializer():
 err: 'rxport->ser.client' dereferencing possible ERR_PTR()

i2c_new_client_device() returns error pointers on failure and in
dev_dbg statement we are dereferencing error pointer which is a bug.

Fix this by using IS_ERR() which checks for error pointers.

Fixes: afe267f2 ("media: i2c: add DS90UB960 driver")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

drivers/media/i2c/ds90ub960.c

@@ -1662,10 +1662,10 @@ static int ub960_rxport_add_serializer(struct ub960_data *priv, u8 nport)
 	ser_info.addr = rxport->ser.alias;
 	rxport->ser.client =
 		i2c_new_client_device(priv->client->adapter, &ser_info);
-	if (!rxport->ser.client) {
+	if (IS_ERR(rxport->ser.client)) {
 		dev_err(dev, "rx%u: cannot add %s i2c device", nport,
 			ser_info.type);
-		return -EIO;
+		return PTR_ERR(rxport->ser.client);
 	}
 
 	dev_dbg(dev, "rx%u: remote serializer at alias 0x%02x (%u-%04x)\n",