drm/virtio: add define for second capset to the virgl code.

Although the kernel doesn't use this, qemu imports these headers
and it's best to keep them consistent.

This define is also something userspace may want to use.
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20180503021021.10694-1-airlied@gmail.comSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

include/uapi/linux/virtio_gpu.h

@@ -260,6 +260,7 @@ struct virtio_gpu_cmd_submit {
 };
 
 #define VIRTIO_GPU_CAPSET_VIRGL 1
+#define VIRTIO_GPU_CAPSET_VIRGL2 2
 
 /* VIRTIO_GPU_CMD_GET_CAPSET_INFO */
 struct virtio_gpu_get_capset_info {