net: udp4: move GSO functions to udp_offload

Similarly to TCP offloading and UDPv6 offloading, move all related
UDPv4 functions to udp_offload.c to make things more explicit. Also,
by this, we can make those functions static.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 7b51429..5598b06 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1566,13 +1566,6 @@
 	.netns_ok =	1,
 };
 
-static const struct net_offload udp_offload = {
-	.callbacks = {
-		.gso_send_check = udp4_ufo_send_check,
-		.gso_segment = udp4_ufo_fragment,
-	},
-};
-
 static const struct net_protocol icmp_protocol = {
 	.handler =	icmp_rcv,
 	.err_handler =	icmp_err,
@@ -1672,7 +1665,7 @@
 	/*
 	 * Add offloads
 	 */
-	if (inet_add_offload(&udp_offload, IPPROTO_UDP) < 0)
+	if (udpv4_offload_init() < 0)
 		pr_crit("%s: Cannot add UDP protocol offload\n", __func__);
 	if (tcpv4_offload_init() < 0)
 		pr_crit("%s: Cannot add TCP protocol offload\n", __func__);