Add vkms support

The vkms driver is used to get the Android to work on the BeagleBone
Black. Only a minimum amount of support is needed but the driver can
only be recognized by looking at card DRM nodes. The vkms driver does
not publish a render node.

We refactored the cros_gralloc_driver::init to test both the render
nodes and the card nodes.

Change-Id: Ie750aa45fc359ba7917919904693b1ab8088ad16
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/2213742
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Commit-Queue: Gurchetan Singh <gurchetansingh@chromium.org>
3 files changed