skmsg: Make __sk_psock_purge_ingress_msg() static

It is only used within skmsg.c so can become static.
Signed-off-by: NCong Wang <cong.wang@bytedance.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NJakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20210223184934.6054-8-xiyou.wangcong@gmail.com

include/linux/skmsg.h

@@ -340,8 +340,6 @@ static inline void sk_psock_free_link(struct sk_psock_link *link)
 
 struct sk_psock_link *sk_psock_link_pop(struct sk_psock *psock);
 
-void __sk_psock_purge_ingress_msg(struct sk_psock *psock);
-
 static inline void sk_psock_cork_free(struct sk_psock *psock)
 {
 	if (psock->cork) {

net/core/skmsg.c

@@ -619,7 +619,7 @@ struct sk_psock_link *sk_psock_link_pop(struct sk_psock *psock)
 	return link;
 }
 
-void __sk_psock_purge_ingress_msg(struct sk_psock *psock)
+static void __sk_psock_purge_ingress_msg(struct sk_psock *psock)
 {
 	struct sk_msg *msg, *tmp;