minigbm/msm: Disable UBWC for video gtest

minigbm/msm: Disable UBWC for video gtest

video_decode_accelerator_tests need non UBWC
frames in order to check for exactness.  This
is expected to be a short term fix until a
proper verification method is devised.

BUG=b:171260705
TEST=YouTube has UBWC, video_decode_accelerator_tests does not

Change-Id: Ia3ab02493f8b740ba9589b4fc21d3fa6b23ea7cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/2523246
Reviewed-by: Fritz Koenig <frkoenig@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@chromium.org>
Tested-by: Fritz Koenig <frkoenig@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Commit-Queue: Gurchetan Singh <gurchetansingh@chromium.org>