Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2020-10-21' into staging

QAPI patches patches for 2020-10-21

# gpg: Signature made Wed 21 Oct 2020 04:01:41 BST
# gpg:                using RSA key 354BC8B3D7EB2A6B68674E5F3870B400EB918653
# gpg:                issuer "armbru@redhat.com"
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>" [full]
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>" [full]
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-qapi-2020-10-21:
  qapi: Restrict Xen migration commands to migration.json
  qapi: Restrict 'query-kvm' command to machine code
  qapi: Restrict '(p)memsave' command to machine code
  qapi: Restrict 'system wakeup/reset/powerdown' commands to machine.json
  qapi: Restrict 'inject-nmi' command to machine code

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