Merge remote-tracking branch 'remotes/kraxel/tags/vga-20200904-pull-request' into staging

vga: fixes for cirrus and virtio-gpu.

# gpg: Signature made Fri 04 Sep 2020 12:26:36 BST
# gpg:                using RSA key 4CB6D8EED3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>" [full]
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>" [full]
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>" [full]
# Primary key fingerprint: A032 8CFF B93A 17A7 9901  FE7D 4CB6 D8EE D3E8 7138

* remotes/kraxel/tags/vga-20200904-pull-request:
  cirrus: handle wraparound in cirrus_invalidate_region
  virtio-gpu: fix unmap the already mapped items

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