virglrenderer: introduce virgl_renderer_resource_map2
Introduce virgl_renderer_resource_map2, a variant of virgl_renderer_resource_map with different semantics, intended to be used by VMMs that run the virtio-gpu device in the same context/process as the VM, enabling them to delegate to virglrenderer the mapping of a BO into a host address that's linked to a guest address.
This function requires MAP_FIXED in flags and must be called with a valid address to be used in mmap(). The address is owned by the VMM and must be released by its own means.
Renderer contexts can optionally implement resource_map() to map OPAQUE_HANDLE blobs on behalf of the VMM. This is specially useful for native context implementations as allows them to honor BO sharing semantics.