minigbm: virtio-gpu: add more supported formats

minigbm: virtio-gpu: add more supported formats

There is a desire to use virtio-gpu + Android with kernel v4.4. Let's
make it like the vgem backend, which aligns widths and heights to
64-pixel boundaries to support LLVM requirements.

BUG=chromium:616275
TEST=no crashes when running Android with amd64-generic-cheets

Change-Id: I5640a0f9cc84260d30eecddd84307170fa41d2ce
Reviewed-on: https://chromium-review.googlesource.com/471879
Commit-Ready: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>