dt-bindings: soc: renesas: Move renesas,prr from arm to soc

The Renesas Product Register DT binding is not a top-level DT binding,
hence it does not belong under Documentation/devicetree/bindings/arm/.
Move it to Documentation/devicetree/bindings/soc/renesas/.

While at it, change the license from GPL-2.0 (only) to GPL-2.0-only OR
BSD-2-Clause, to match common practices.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Simon Horman <horms@verge.net.au>
Link: https://lore.kernel.org/r/5f124fc332b4b866f5238ada7ac000f4639c88c3.1651495078.git.geert+renesas@glider.be

Documentation/devicetree/bindings/arm/renesas,prr.yaml → Documentation/devicetree/bindings/soc/renesas/renesas,prr.yaml

-# SPDX-License-Identifier: GPL-2.0
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 %YAML 1.2
 ---
-$id: http://devicetree.org/schemas/arm/renesas,prr.yaml#
+$id: http://devicetree.org/schemas/soc/renesas/renesas,prr.yaml#
 $schema: http://devicetree.org/meta-schemas/core.yaml#
 
 title: Renesas Product Register