minigbm: rockchip: align to 128 bytes

minigbm: rockchip: align to 128 bytes

cmemp_heap_partition in the mali driver checks if every plane is
64-byte aligned. Since we expose a fd for every plane in the
cros gralloc handle, we hit this case. We need to enforce this
alignment on our YV12 allocations.

BUG=chromium:616275
TEST=
android.media.cts.VideoEncoderTest#testGoogH264FlexArbitraryH

passes on veyron_minnie-cheets.

Change-Id: If6375eddd18fd216e7f07eb2cc47090d838f82ab
Reviewed-on: https://chromium-review.googlesource.com/459104
Commit-Ready: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>