minigbm: i915: add XR30 and XB30 formats.

minigbm: i915: add XR30 and XB30 formats.

i915 supports 30bit per component formats.
This CL adds XR30 and XB30 to minigbm i915 backend.

This CL also sorts render_target_formats alphabetically.

BUG=chromium:776093
TEST=Ran a modifier version of null_platform_test that will be
uploaded soon.

Change-Id: If4f2f74cb10a0534023b9b6142ee84ced0ed8a38
Reviewed-on: https://chromium-review.googlesource.com/726318
Commit-Ready: Daniele Castagna <dcastagna@chromium.org>
Tested-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>