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 <[e-mail]>
Signed-off-by: Casey Schaufler <[e-mail]>

security/smack/smack_lsm.c

···
 #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: