unix: define and set show_fdinfo only if procfs is enabled

Follow the pattern used with other *_show_fdinfo functions and only
define unix_show_fdinfo and set it in proto_ops if CONFIG_PROCFS
is set.

Fixes: 3c32da19a8 ("unix: Show number of pending scm files of receive queue in fdinfo")
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/unix/af_unix.c

@@ -682,6 +682,7 @@ static int unix_set_peek_off(struct sock *sk, int val)
 	return 0;
 }
 
+#ifdef CONFIG_PROCFS
 static void unix_show_fdinfo(struct seq_file *m, struct socket *sock)
 {
 	struct sock *sk = sock->sk;
@@ -692,6 +693,9 @@ static void unix_show_fdinfo(struct seq_file *m, struct socket *sock)
 		seq_printf(m, "scm_fds: %u\n", READ_ONCE(u->scm_stat.nr_fds));
 	}
 }
+#else
+#define unix_show_fdinfo NULL
+#endif
 
 static const struct proto_ops unix_stream_ops = {
 	.family =	PF_UNIX,