gpu_renderer: Enable DRM_FORMAT_RGB565 format.
gpu_renderer: Enable DRM_FORMAT_RGB565 format.

Some games under arcvm tried to create gbu buffer in this format.

BUG=b:128019372
TEST=manual - Run Asphalt 8 in ARCVM.

Change-Id: I12e67981b4a0b50574ff57cd6bfe94c042feedac
Reviewed-on: https://chromium-review.googlesource.com/1518731
Commit-Ready: ChromeOS CL Exonerator Bot <fa429e5907f00867f797423aea74327bb02c91b6@appspot.gserviceaccount.com>
Tested-by: Lepton Wu <98fe55dd9d3c1cbbf1dc9faf0be9e8ebf7fc5bb6@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Zach Reizner <3374927928a53d04457674c546bd4de57c2044ec@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm