arm/rockchip.yaml - many separate entries instead of enums

[Krzysztof Kozlowski]

Hi Heiko,

I found that Documentation/devicetree/bindings/arm/rockchip.yaml uses
pattern of one board per item in oneOf.

This leads to quite big file, with many entries, although gives nice
description for each board.

I find enum-based pattern, like FSL [1], much more readable and compact.
What do you think? I could re-organize the arm/rockchip.yaml, but I
don't want to mess with your preference.

[1]
https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/arm/fsl.yaml#L191

Best regards,
Krzysztof