minigbm: use drv_array for combinations and kms_items

This de-deuplicates the various dynamic arrays we use.

BUG=chromium:764871
TEST=gbmtest passes

Change-Id: I94c8cf7c71fdb98b931aab00c5381853e2ae0d3f
Reviewed-on: https://chromium-review.googlesource.com/758149
Commit-Ready: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
6 files changed