md: Disable bad blocks and v0.90 metadata.

v0.90 metadata cannot record bad blocks, so when loading metadata
for such a device, set shift to -1.
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/md.c

@@ -1058,6 +1058,7 @@ static int super_90_load(mdk_rdev_t *rdev, mdk_rdev_t *refdev, int minor_version
 	rdev->preferred_minor = sb->md_minor;
 	rdev->data_offset = 0;
 	rdev->sb_size = MD_SB_BYTES;
+	rdev->badblocks.shift = -1;
 
 	if (sb->level == LEVEL_MULTIPATH)
 		rdev->desc_nr = -1;
@@ -3004,6 +3005,9 @@ static mdk_rdev_t *md_import_device(dev_t newdev, int super_format, int super_mi
 			goto abort_free;
 		}
 	}
+	if (super_format == -1)
+		/* hot-add for 0.90, or non-persistent: so no badblocks */
+		rdev->badblocks.shift = -1;
 
 	return rdev;