Align the name of operating-points node to dtschema to fix warnings like:

  arch/arm64/boot/dts/exynos/exynos5433-tm2.dt.yaml:
    opp-table2: $nodename:0: 'opp-table2' does not match '^opp-table(-[a-z0-9]+)?$'
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Link: https://lore.kernel.org/r/20210820081458.83406-1-krzysztof.kozlowski@canonical.com