ipv6: move udp declarations to net/udp.h

Fix the following compilation warning:

net/ipv6/udp.c:1031:30: warning: no previous prototype for 'udp_v6_early_demux' [-Wmissing-prototypes]
1031 | INDIRECT_CALLABLE_SCOPE void udp_v6_early_demux(struct sk_buff *skb)
| ^~~~~~~~~~~~~~~~~~
net/ipv6/udp.c:1072:29: warning: no previous prototype for 'udpv6_rcv' [-Wmissing-prototypes]
1072 | INDIRECT_CALLABLE_SCOPE int udpv6_rcv(struct sk_buff *skb)
| ^~~~~~~~~

Signed-off-by: Leon Romanovsky <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/udp.h

···
 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));
+INDIRECT_CALLABLE_DECLARE(void udp_v6_early_demux(struct sk_buff *));
+INDIRECT_CALLABLE_DECLARE(int udpv6_rcv(struct sk_buff *));
+
 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);

net/ipv6/ip6_input.c

···
 
 #include <net/sock.h>
 #include <net/snmp.h>
+#include <net/udp.h>
 
 #include <net/ipv6.h>
 #include <net/protocol.h>
···
 #include <net/inet_ecn.h>
 #include <net/dst_metadata.h>
 
-INDIRECT_CALLABLE_DECLARE(void udp_v6_early_demux(struct sk_buff *));
 INDIRECT_CALLABLE_DECLARE(void tcp_v6_early_demux(struct sk_buff *));
 static void ip6_rcv_finish_core(struct net *net, struct sock *sk,
 				struct sk_buff *skb)
···
 		ip6_sublist_rcv(&sublist, curr_dev, curr_net);
 }
 
-INDIRECT_CALLABLE_DECLARE(int udpv6_rcv(struct sk_buff *));
 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));
 
 /*