minigbm: add BO_USE_TEXTURE

minigbm: add BO_USE_TEXTURE

Many people have requested re-adding BO_USE_TEXTURE as a flag
since:

BO_USE_RENDERING means the buffer will be used as a render target.
BO_USE_TEXTURE means the buffer will be textured from.

BUG=chromium:616275
TEST=minigbm/arc-cros-gralloc compiles

Change-Id: I63be6682cf4e2415dc42c78b2cab3ad694bcd818
Reviewed-on: https://chromium-review.googlesource.com/448251
Commit-Ready: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>