arm64: dts: renesas: Fix operating point table node names

Align the node names of device nodes representing operating point v2
tables with the expectations of the DT bindings in
Documentation/devicetree/bindings/opp/opp-v2.yaml.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/ac885456ffb00fa4cc4069b9967761df2c98c3d8.1637764588.git.geert+renesas@glider.be