Raspberry Pi Official 7" Touchscreen unsupported

[fhunleth]

See https://elixirforum.com/t/raspberry-pi-5-and-the-official-7-display-weston-refusing-to-start-because-of-missing-drivers/69100/5

The summary is that Mesa3D needs to be updated and there's a patch working its way through the Buildroot patch queue to do that.