null_platform_test: Support specifying CRTC index

Some platforms support different modifiers on different CRTCs. Allow
specifying that.

BUG=none
TEST=null_platform_test --crtc_index 1

Change-Id: Iea15ea5bb5eec169923c8c30d81c1feb92ba0931
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/drm-tests/+/3462924
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
Commit-Queue: Brian Norris <briannorris@chromium.org>
Reviewed-by: Po-Hsien Wang <pwang@chromium.org>
1 file changed