dt-bindings: gpu: mali-utgard: Add Rockchip Utgard Malis

Some (older or lower power) Rockchip socs use Utgard-based Mali-GPUs.
So add the necessary compatibles for them. As the setup is the same for
all of them (needing only the additional reset line), they get added in
a somewhat condensed form, to not inflate the document unnecessary.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Rob Herring <robh@kernel.org>