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: Paul Durrant <[e-mail]>
Signed-off-by: Boris Ostrovsky <[e-mail]>

drivers/xen/privcmd.c

···
 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) {
···
 		break;
 
 	default:
-		ret = -EINVAL;
 		break;
 	}