minigbm: Added gralloc API to internal API

minigbm: Added gralloc API to internal API

Added the drv analogues of the 2 flexible formats we need to support.
Added analogues of most of the gralloc use flags, except:

GRALLOC_USAGE_SW_READ_MASK
GRALLOC_USAGE_SW_WRITE_MASK
GRALLOC_USAGE_HW_MASK
GRALLOC_USAGE_FOREIGN_BUFFERS
GRALLOC_USAGE_ALLOC_MASK

These are used as masks and don't make sense as usage hints.  In
addition, put the new flags in the drivers' supported lists and
added a flexible format query function.

BUG=chromium:616275
TEST=minigbm still builds
CQ-DEPEND=CL:371501

Change-Id: Idd2ecd6fde3e6c5caaaf3a8404d0d7db20b4ecf4
Reviewed-on: https://chromium-review.googlesource.com/372359
Commit-Ready: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>