Merge remote-tracking branch 'remotes/kraxel/tags/vga-20210916-pull-request' into staging

virtio-gpu + ui: fence syncronization.
qxl: unbreak live migration.

# gpg: Signature made Thu 16 Sep 2021 06:56:03 BST
# gpg:                using RSA key A0328CFFB93A17A79901FE7D4CB6D8EED3E87138
# 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-20210916-pull-request:
  virtio-gpu: Add gl_flushed callback
  ui/gtk-egl: Wait for the draw signal for dmabuf blobs
  ui: Create sync objects and fences only for blobs
  ui/egl: Add egl helpers to help with synchronization
  ui/gtk: Create a common release_dmabuf helper
  qxl: fix pre-save logic

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