KMS seems broken in vc4.ko

[Ryutaroh Matsumoto]

> In the above dmesg output, we have
> [  148.180685] [drm:drm_ioctl [drm]] comm="kmscube" pid=1926, dev=0xe200, auth=1, VC4_GET_PARAM
> [  148.180716] [drm:drm_ioctl [drm]] comm="kmscube", pid=1926, ret=-19
> Is the failure of VC4_GET_PARAM expected and normal???

The codes at
https://elixir.bootlin.com/linux/v5.10.19/source/drivers/gpu/drm/vc4/vc4_drv.c#L77
	if (!vc4->v3d)
		return -ENODEV;
seems to cause failure of VC4_GET_PARAM.
It is funny that even on Raspberry Pi OS, VC4_GET_PARAM fails in the same way,
where v3d must exist there.

Ryutaroh