dm ioctl: use uninitialized_var

drivers/md/dm-ioctl.c:1405: warning: 'param' may be used uninitialized in this function

Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Alasdair G Kergon <[e-mail]>

drivers/md/dm-ioctl.c

···
 {
 	int r = 0;
 	unsigned int cmd;
-	struct dm_ioctl *param;
+	struct dm_ioctl *uninitialized_var(param);
 	ioctl_fn fn = NULL;
 	size_t param_size;