tun: Return -EINVAL if neither IFF_TUN nor IFF_TAP is set.

After commit 2b980dbd
("lsm: Add hooks to the TUN driver") tun_set_iff doesn't
return -EINVAL though neither IFF_TUN nor IFF_TAP is set.
Signed-off-by: Kusanagi Kouichi <slash@ma.neweb.ne.jp>
Reviewed-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tun.c

@@ -946,8 +946,6 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 		char *name;
 		unsigned long flags = 0;
 
-		err = -EINVAL;
-
 		if (!capable(CAP_NET_ADMIN))
 			return -EPERM;
 		err = security_tun_dev_create();
@@ -964,7 +962,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 			flags |= TUN_TAP_DEV;
 			name = "tap%d";
 		} else
-			goto failed;
+			return -EINVAL;
 
 		if (*ifr->ifr_name)
 			name = ifr->ifr_name;