Merge tag 'migration-20240407-pull-request' of https://gitlab.com/peterx/qemu into staging

Migration pull for 9.0-rc3

- Wei/Lei's fix on a rare postcopy race that can hang the channel (since 8.0)
- Avihai's fix on maintainers file, points to the right doc links

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* tag 'migration-20240407-pull-request' of https://gitlab.com/peterx/qemu:
  MAINTAINERS: Adjust migration documentation files
  migration/postcopy: ensure preempt channel is ready before loading states

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>