cros_gralloc: Handle failure to get prime fd

... in cros_gralloc_driver::allocate().

BUG=b:178495907
TEST=Cuttlefish CFI

Change-Id: Ibb9a5e55f2d2a4bf6be71f03dfe3f0fcd55a1b55
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/2658929
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Commit-Queue: Gurchetan Singh <gurchetansingh@chromium.org>
6 files changed