Smack: fix dereferenced before check

This patch fixes the warning reported by smatch:
security/smack/smack_lsm.c:2872 smack_socket_connect() warn:
variable dereferenced before check 'sock->sk' (see line 2869)
Signed-off-by: Vasyl Gomonovych <gomonovych@gmail.com>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

security/smack/smack_lsm.c

@@ -2866,12 +2866,16 @@ static int smack_socket_connect(struct socket *sock, struct sockaddr *sap,
 #endif
 #ifdef SMACK_IPV6_SECMARK_LABELING
 	struct smack_known *rsp;
-	struct socket_smack *ssp = sock->sk->sk_security;
+	struct socket_smack *ssp;
 #endif
 
 	if (sock->sk == NULL)
 		return 0;
 
+#ifdef SMACK_IPV6_SECMARK_LABELING
+	ssp = sock->sk->sk_security;
+#endif
+
 	switch (sock->sk->sk_family) {
 	case PF_INET:
 		if (addrlen < sizeof(struct sockaddr_in))