udp: move gro declarations to net/udp.h

This removes following warnings :
  CC      net/ipv4/udp_offload.o
net/ipv4/udp_offload.c:504:17: warning: no previous prototype for 'udp4_gro_receive' [-Wmissing-prototypes]
  504 | struct sk_buff *udp4_gro_receive(struct list_head *head, struct sk_buff *skb)
      |                 ^~~~~~~~~~~~~~~~
net/ipv4/udp_offload.c:584:29: warning: no previous prototype for 'udp4_gro_complete' [-Wmissing-prototypes]
  584 | INDIRECT_CALLABLE_SCOPE int udp4_gro_complete(struct sk_buff *skb, int nhoff)
      |                             ^~~~~~~~~~~~~~~~~

  CHECK   net/ipv6/udp_offload.c
net/ipv6/udp_offload.c:115:16: warning: symbol 'udp6_gro_receive' was not declared. Should it be static?
net/ipv6/udp_offload.c:148:29: warning: symbol 'udp6_gro_complete' was not declared. Should it be static?
  CC      net/ipv6/udp_offload.o
net/ipv6/udp_offload.c:115:17: warning: no previous prototype for 'udp6_gro_receive' [-Wmissing-prototypes]
  115 | struct sk_buff *udp6_gro_receive(struct list_head *head, struct sk_buff *skb)
      |                 ^~~~~~~~~~~~~~~~
net/ipv6/udp_offload.c:148:29: warning: no previous prototype for 'udp6_gro_complete' [-Wmissing-prototypes]
  148 | INDIRECT_CALLABLE_SCOPE int udp6_gro_complete(struct sk_buff *skb, int nhoff)
      |                             ^~~~~~~~~~~~~~~~~
Signed-off-by: Eric Dumazet <edumazet@google.com>

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/udp.h b/include/net/udp.h
index a8fa6c0..5a2d677 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -27,6 +27,7 @@
 #include <linux/ipv6.h>
 #include <linux/seq_file.h>
 #include <linux/poll.h>
+#include <linux/indirect_call_wrapper.h>
 
 /**
  *	struct udp_skb_cb  -  UDP(-Lite) private variables
@@ -166,6 +167,12 @@ static inline void udp_csum_pull_header(struct sk_buff *skb)
 typedef struct sock *(*udp_lookup_t)(struct sk_buff *skb, __be16 sport,
 				     __be16 dport);
 
+INDIRECT_CALLABLE_DECLARE(struct sk_buff *udp4_gro_receive(struct list_head *,
+							   struct sk_buff *));
+INDIRECT_CALLABLE_DECLARE(int udp4_gro_complete(struct sk_buff *, int));
+INDIRECT_CALLABLE_DECLARE(struct sk_buff *udp6_gro_receive(struct list_head *,
+							   struct sk_buff *));
+INDIRECT_CALLABLE_DECLARE(int udp6_gro_complete(struct sk_buff *, int));
 struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
 				struct udphdr *uh, struct sock *sk);
 int udp_gro_complete(struct sk_buff *skb, int nhoff, udp_lookup_t lookup);