tcp: md5: tcp_md5_do_lookup_exact() can be static

Fixes: 6797318e ("tcp: md5: add an address prefix for key lookup")
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_ipv4.c

@@ -943,7 +943,7 @@ struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
 }
 EXPORT_SYMBOL(tcp_md5_do_lookup);
 
-struct tcp_md5sig_key *tcp_md5_do_lookup_exact(const struct sock *sk,
+static struct tcp_md5sig_key *tcp_md5_do_lookup_exact(const struct sock *sk,
 						      const union tcp_md5_addr *addr,
 						      int family, u8 prefixlen)
 {