drm: Update vdrm structs
Plus misc drm/msm patch.
I realized I'd forgotten to put up an MR with the virglrender side matching mesa/mesa@b9024477
I'm starting to think there is also room to have a common drm_context "base class" and helpers to share a bit more code with the other vdrm/nctx implementations. But I can hold off if that would be too disruptive for the in-flight vdrm implementations.