dm: eliminate potential source of excessive kernel log noise

There wasn't ever a real need to log an error in the kernel log for
ioctls issued with insufficient permissions. Simply return an error
and if an admin/user is sufficiently motivated they can enable DM's
dynamic debugging to see an explanation for why the ioctls were
disallowed.
Reported-by: Nir Soffer <nsoffer@redhat.com>
Fixes: e980f623 ("dm: don't allow ioctls to targets that don't map to whole devices")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm.c

@@ -562,7 +562,7 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
 		 * subset of the parent bdev; require extra privileges.
 		 */
 		if (!capable(CAP_SYS_RAWIO)) {
-			DMWARN_LIMIT(
+			DMDEBUG_LIMIT(
 	"%s: sending ioctl %x to DM device without required privilege.",
 				current->comm, cmd);
 			r = -ENOIOCTLCMD;