cirrus: add support for GBM_FORMAT_ARGB8888 and GBM_FORMAT_XRGB8888

Cirrus supports both formats for scanout and EGL+llvmpipe requires it.
Cirrus+llvmpipe is still used for running Chrome OS in a VM, so GBM
needs to support allocating BOs of the required format for rendering.

TEST=ui works in VM
BUG=chromium:588140

Change-Id: Ibc834c334f54e9a36173285d18c0aa97de58fdb6
Reviewed-on: https://chromium-review.googlesource.com/328750
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
1 file changed