Pull MD fixes from Song:

"This set contains two fixes for old issues (by Neil) and one fix
 for 6.3 (by Xiao)."

* 'md-fixes' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md: select BLOCK_LEGACY_AUTOLOAD
  md: avoid signed overflow in slot_store()
  md: Free resources in __md_stop