[PPPoX/E]: return ENOTTY on unknown ioctl requests

here another patch for the PPPoX/E code that makes sure that ENOTTY is
returned for unknown ioctl requests rather than 0 (and removes another
unneeded initializer which I didn't bother creating a separate patch for).

Signed-off-by: Florian Zumbiehl <florz@florz.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/pppoe.c b/drivers/net/pppoe.c
index 6f98834..f75aeaa 100644
--- a/drivers/net/pppoe.c
+++ b/drivers/net/pppoe.c
@@ -664,8 +664,8 @@
 {
 	struct sock *sk = sock->sk;
 	struct pppox_sock *po = pppox_sk(sk);
-	int val = 0;
-	int err = 0;
+	int val;
+	int err;
 
 	switch (cmd) {
 	case PPPIOCGMRU:
@@ -754,8 +754,9 @@
 		err = 0;
 		break;
 
-	default:;
-	};
+	default:
+		err = -ENOTTY;
+	}
 
 	return err;
 }