minigbm: tweak cros-gralloc flags

minigbm: tweak cros-gralloc flags

The Play Store wants a ABGR8888 HW cursor, and we can't in
general support this, so let's ignore the cursor flag rather
than fail the allocation.

We also interpret GRALLOC_USAGE_HW_COMPOSER as BO_USE_SCANOUT
| BO_USE_RENDERING. This fails with YV12, since we can't scanout
from it on Intel/Mediatek. Let's first try to allocate with the
scanout flag enabled and then fall-back to rendering if it's
not supported (i.e, first try overlay but then try OpenGL).

In addition, let's interpret GRALLOC_USAGE_HW_FB the same as
GRALLOC_USAGE_HW_COMPOSER since the framebuffer device
(Chrome in our case) wants to scanout but can also fall back.

BUG=chromium:616275
TEST=run cts --package com.drawelements.deqp.egl on minnie
CQ-DEPEND=CL:414536

Change-Id: I57cd681ca8ff0186698bd0a046c3a7b346f3e434
Reviewed-on: https://chromium-review.googlesource.com/414537
Commit-Ready: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>