xdp: fix uninitialized 'err' variable

Smatch caught an uninitialized variable error which GCC seems
to miss.

Fixes: a25717d2 ("xdp: support simultaneous driver and hw XDP attachment")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -1414,14 +1414,17 @@ static int rtnl_xdp_fill(struct sk_buff *skb, struct net_device *dev)
 
 	prog_id = 0;
 	mode = XDP_ATTACHED_NONE;
-	if (rtnl_xdp_report_one(skb, dev, &prog_id, &mode, XDP_ATTACHED_SKB,
-				IFLA_XDP_SKB_PROG_ID, rtnl_xdp_prog_skb))
+	err = rtnl_xdp_report_one(skb, dev, &prog_id, &mode, XDP_ATTACHED_SKB,
+				  IFLA_XDP_SKB_PROG_ID, rtnl_xdp_prog_skb);
+	if (err)
 		goto err_cancel;
-	if (rtnl_xdp_report_one(skb, dev, &prog_id, &mode, XDP_ATTACHED_DRV,
-				IFLA_XDP_DRV_PROG_ID, rtnl_xdp_prog_drv))
+	err = rtnl_xdp_report_one(skb, dev, &prog_id, &mode, XDP_ATTACHED_DRV,
+				  IFLA_XDP_DRV_PROG_ID, rtnl_xdp_prog_drv);
+	if (err)
 		goto err_cancel;
-	if (rtnl_xdp_report_one(skb, dev, &prog_id, &mode, XDP_ATTACHED_HW,
-				IFLA_XDP_HW_PROG_ID, rtnl_xdp_prog_hw))
+	err = rtnl_xdp_report_one(skb, dev, &prog_id, &mode, XDP_ATTACHED_HW,
+				  IFLA_XDP_HW_PROG_ID, rtnl_xdp_prog_hw);
+	if (err)
 		goto err_cancel;
 
 	err = nla_put_u8(skb, IFLA_XDP_ATTACHED, mode);