arm64: dts: rockchip: Add node for gpu on rk3399-roc-pc

rk3399-roc-pc has a Mali gpu, enable it for use with panfrost and mesa >19.2.

Signed-off-by: Markus Reichl <m.reichl@fivetechno.de>
Link: https://lore.kernel.org/r/c2b88509-129d-46d4-9e23-15d0482951be@fivetechno.de


Signed-off-by: Heiko Stuebner <heiko@sntech.de>