security/smack: remove unused varible 'rc'

This varible isn't used and can be removed to avoid a gcc warning:
security/smack/smack_lsm.c:3873:6: warning: variable ‘rc’ set but not
used [-Wunused-but-set-variable]

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-security-module@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

security/smack/smack_lsm.c

@@ -3870,7 +3870,6 @@ static struct smack_known *smack_from_netlbl(struct sock *sk, u16 family,
 	struct netlbl_lsm_secattr secattr;
 	struct socket_smack *ssp = NULL;
 	struct smack_known *skp = NULL;
-	int rc;
 
 	netlbl_secattr_init(&secattr);
 
@@ -3880,7 +3879,7 @@ static struct smack_known *smack_from_netlbl(struct sock *sk, u16 family,
 	if (netlbl_skbuff_getattr(skb, family, &secattr) == 0) {
 		skp = smack_from_secattr(&secattr, ssp);
 		if (secattr.flags & NETLBL_SECATTR_CACHEABLE)
-			rc = netlbl_cache_add(skb, family, &skp->smk_netlabel);
+			netlbl_cache_add(skb, family, &skp->smk_netlabel);
 	}
 
 	netlbl_secattr_destroy(&secattr);