Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2022-02-28' into staging

QAPI patches patches for 2022-02-28

# gpg: Signature made Mon 28 Feb 2022 10:40:22 GMT
# 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-2022-02-28:
  qapi: Belatedly adjust limitations documentation
  rtc: Have event RTC_CHANGE identify the RTC by QOM path
  hw/rtc: Compile pl031 once-only
  qapi: Document some missing details of RTC_CHANGE event
  qapi: Move RTC_CHANGE back out of target schema
  qapi/migration: Fix examples document wrong field name for arguments
  qapi: Fix stale reference to scripts/qapi.py in a comment
  keyval: Fix grammar comment to cover downstream prefix
  scripts/qapi: minor delinting

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