xen/privcmd: return -ENOTTY for unimplemented IOCTLs

The code sets the default return code to -ENOSYS but then overrides this
to -EINVAL in the switch() statement's default case, which is clearly
silly.

This patch removes the override and sets the default return code to
-ENOTTY, which is the conventional return for an unimplemented ioctl.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Signed-off-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>

drivers/xen/privcmd.c

@@ -551,7 +551,7 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
 static long privcmd_ioctl(struct file *file,
 			  unsigned int cmd, unsigned long data)
 {
-	int ret = -ENOSYS;
+	int ret = -ENOTTY;
 	void __user *udata = (void __user *) data;
 
 	switch (cmd) {
@@ -572,7 +572,6 @@ static long privcmd_ioctl(struct file *file,
 		break;
 
 	default:
-		ret = -EINVAL;
 		break;
 	}