Merge remote-tracking branch 'remotes/cohuck-gitlab/tags/s390x-20210520-v2' into staging

s390x fixes and cleanups; also related fixes in xtensa,
arm, and x86 code

# gpg: Signature made Thu 20 May 2021 13:23:15 BST
# gpg:                using RSA key C3D0D66DC3624FF6A8C018CEDECF6B93C6F02FAF
# gpg:                issuer "cohuck@redhat.com"
# gpg: Good signature from "Cornelia Huck <conny@cornelia-huck.de>" [unknown]
# gpg:                 aka "Cornelia Huck <huckc@linux.vnet.ibm.com>" [full]
# gpg:                 aka "Cornelia Huck <cornelia.huck@de.ibm.com>" [full]
# gpg:                 aka "Cornelia Huck <cohuck@kernel.org>" [unknown]
# gpg:                 aka "Cornelia Huck <cohuck@redhat.com>" [unknown]
# Primary key fingerprint: C3D0 D66D C362 4FF6 A8C0  18CE DECF 6B93 C6F0 2FAF

* remotes/cohuck-gitlab/tags/s390x-20210520-v2:
  tests/tcg/x86_64: add vsyscall smoke test
  target/i386: Make sure that vsyscall's tb->size != 0
  vfio-ccw: Attempt to clean up all IRQs on error
  hw/s390x/ccw: Register qbus type in abstract TYPE_CCW_DEVICE parent
  vfio-ccw: Permit missing IRQs
  accel/tcg: Assert that tb->size != 0 after translation
  target/xtensa: Make sure that tb->size != 0
  target/arm: Make sure that commpage's tb->size != 0
  target/s390x: Fix translation exception on illegal instruction

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