arm64: dts: rockchip: enable gpu on Qnap-TS433

The TS433 doesn't provide display output, but the gpu nevertheless can be
used for compute tasks for example.

So there is no reason not to enable it.

Tested-by: Uwe Kleine-König <ukleinek@debian.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20240723195538.1133436-14-heiko@sntech.de