Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20200618' into staging

s390x update:
- update Linux headers to 5.8-rc1 (for vfio-ccw path handling)
- vfio-ccw: add support for path handling
- documentation fix

# gpg: Signature made Thu 18 Jun 2020 16:36:04 BST
# gpg:                using RSA key C3D0D66DC3624FF6A8C018CEDECF6B93C6F02FAF
# gpg:                issuer "cohuck@redhat.com"
# gpg: Good signature from "Cornelia Huck <conny@cornelia-huck.de>" [marginal]
# 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>" [marginal]
# gpg:                 aka "Cornelia Huck <cohuck@redhat.com>" [marginal]
# Primary key fingerprint: C3D0 D66D C362 4FF6 A8C0  18CE DECF 6B93 C6F0 2FAF

* remotes/cohuck/tags/s390x-20200618:
  docs/s390x: fix vfio-ap device_del description
  vfio-ccw: Add support for the CRW region and IRQ
  s390x/css: Refactor the css_queue_crw() routine
  vfio-ccw: Refactor ccw irq handler
  vfio-ccw: Add support for the schib region
  vfio-ccw: Refactor cleanup of regions
  Linux headers: update

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