cros_gralloc: Fix PlaneLayout width/height metadata

cros_gralloc: Fix PlaneLayout width/height metadata

... by using the horizontal/vertical subsampling of
each plane.

BUG=b:171019648
TEST=vts -m VtsHalGraphicsMapperV4_0TargetTest

Change-Id: I3eccfa1c0ac30394314c83b54ca50d690c679724
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/2503481
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Jason Macnak <natsu@google.com>
Auto-Submit: Jason Macnak <natsu@google.com>
Commit-Queue: Jason Macnak <natsu@google.com>