goldfish-opengl: nuke use std::optional

Although this builds, we could also use the fact
DRM_FORMAT_INVALID is zero and eventually refactor
the gralloc helper out of the HostConnection.

BUG=None
TEST=meson amd64-build/
     ninja -C amd64-build/

Change-Id: I5801abe78fee472652f507be07f27c761dd4dd94
3 files changed