net-tcp_bbr: v2: fix build to prevent no previous prototype for 'bbr2…

…_main' warning

Co-authored-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Alexandre Frade <kernel@xanmod.org>

net/ipv4/tcp_bbr2.c

@@ -2231,7 +2231,7 @@ static bool bbr2_fast_path(struct sock *sk, bool *update_model,
 	return false;
 }
 
-void bbr2_main(struct sock *sk, const struct rate_sample *rs)
+static void bbr2_main(struct sock *sk, const struct rate_sample *rs)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct bbr *bbr = inet_csk_ca(sk);