Most function parameters in virglrenderer.h are opaque to the callers
(i.e., VMMs). Their definitions can be found in virglrenderer_hw.h.
In this commit, virglrenderer_hw.h simply includes virgl_hw.h.
virgl_hw.h is considered legacy however. New definitions that are not
virgl-specific will go into virglrenderer_hw.h.
Signed-off-by: Chia-I Wu <olvaffe@gmail.com>