sock: Introduce named constants for sk_reuse

Name them in a "backward compatible" manner, i.e. reuse or not
are still 1 and 0 respectively. The reuse value of 2 means that
the socket with it will forcibly reuse everyone else's port.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 3744c1c..c8f7aee 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -350,7 +350,7 @@
 	err = 0;
 	sk->sk_no_check = answer_no_check;
 	if (INET_PROTOSW_REUSE & answer_flags)
-		sk->sk_reuse = 1;
+		sk->sk_reuse = SK_CAN_REUSE;
 
 	inet = inet_sk(sk);
 	inet->is_icsk = (INET_PROTOSW_ICSK & answer_flags) != 0;