minigbm: virtgpu: add virgl_protocol.h, add external directory
This adds Mesa protocol headers for BLOB resources. Also some
code movement. See:
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4821
for another example.
BUG=chromium:924405
TEST=compile
Change-Id: I330851e6a58d4e12be8e0e882a230a1cca83e7a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/
1804828
Reviewed-by: Jason Macnak <natsu@google.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Commit-Queue: Gurchetan Singh <gurchetansingh@chromium.org>