arm64: dts: rockchip: remove px30 default optee node

Having a default optee node in a soc devicetree is not really good.
For one there is no guarantee that any tee got loaded and there's even
the possibility that a completely different TEE got loaded.

OP-Tee however will insert relevant nodes to the devicetree (firmware
+reserved memory sections) during its own startup, so there really is
no need to provide a default node.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20191023224409.3550-1-heiko@sntech.de