Merge remote-tracking branch 'remotes/kraxel/tags/vga-20200915-pull-request' into staging

vga: fix qxl modular build.
vga: add support for virtio-gpu modular builds.

# gpg: Signature made Tue 15 Sep 2020 14:08:53 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-20200915-pull-request:
  virtio-gpu: build modular
  virtio-gpu: make virtio_gpu_ops static
  object_initialize: try module load
  meson: remove duplicate qxl sources
  meson: fix module config
  meson: fix qxl dependencies

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