libbpf: Move __dump_nlmsg_t from API to implementation

This typedef is used only by implementation in netlink.c. Nothing uses
it in public API. Move it to netlink.c.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/lib/bpf/libbpf.h

@@ -304,11 +304,8 @@ int bpf_perf_event_read_simple(void *mem, unsigned long size,
 			       void **buf, size_t *buf_len,
 			       bpf_perf_event_print_t fn, void *priv);
 
-struct nlmsghdr;
 struct nlattr;
 typedef int (*dump_nlmsg_t)(void *cookie, void *msg, struct nlattr **tb);
-typedef int (*__dump_nlmsg_t)(struct nlmsghdr *nlmsg, dump_nlmsg_t,
-			      void *cookie);
 int bpf_netlink_open(unsigned int *nl_pid);
 int nl_get_link(int sock, unsigned int nl_pid, dump_nlmsg_t dump_link_nlmsg,
 		void *cookie);

tools/lib/bpf/netlink.c

@@ -18,6 +18,9 @@
 #define SOL_NETLINK 270
 #endif
 
+typedef int (*__dump_nlmsg_t)(struct nlmsghdr *nlmsg, dump_nlmsg_t,
+			      void *cookie);
+
 int bpf_netlink_open(__u32 *nl_pid)
 {
 	struct sockaddr_nl sa;