minigbm: amdgpu: Add formats R8, GR88

minigbm: amdgpu: Add formats R8, GR88

Add R8 and GR88 format for dma_bufs in amdgpu.
Required to support native GMB video playback.
If native GMB is enbaled,chrome transcodes NV12 to
RGB by importing Y plane as R8 EGLImage and the UV plane as GR88 EGLImage.

BUG=b:65302612
TEST=Boot Kahlee with --enable-native-gpu-memory-buffers and play youtube.

Change-Id: Ifa7e50959bb5417088357a0c0aa3ac874ecf6fc9
Signed-off-by: Deepak Sharma <deepak.sharma@amd.com>
Reviewed-on: https://chromium-review.googlesource.com/695850
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>