[XFRM] xfrm_user: Fix return values of xfrm_add_sa_expire.

As noted by Kent Yoder, this function will always return an
error. Make sure it returns zero on success.

Signed-off-by: David S. Miller <[e-mail]>

net/xfrm/xfrm_user.c

···
 	struct xfrm_usersa_info *p = &ue->state;
 
 	x = xfrm_state_lookup(&p->id.daddr, p->id.spi, p->id.proto, p->family);
-		err = -ENOENT;
 
+	err = -ENOENT;
 	if (x == NULL)
 		return err;
 
-	err = -EINVAL;
-
 	spin_lock_bh(&x->lock);
+	err = -EINVAL;
 	if (x->km.state != XFRM_STATE_VALID)
 		goto out;
 	km_state_expired(x, ue->hard, current->pid);
···
 		xfrm_audit_log(NETLINK_CB(skb).loginuid, NETLINK_CB(skb).sid,
 			       AUDIT_MAC_IPSEC_DELSA, 1, NULL, x);
 	}
+	err = 0;
 out:
 	spin_unlock_bh(&x->lock);
 	xfrm_state_put(x);