nvif_head_ctor
ret = nvif_head_ctor(&disp->disp, nv_crtc->base.name, nv_crtc->index, &nv_crtc->head);
ret = nvif_head_ctor(disp->disp, head->base.base.name, head->base.index, &head->base.head);
int nvif_head_ctor(struct nvif_disp *, const char *name, int id, struct nvif_head *);