ARM: dts: stih418: align OPP table names with DT schema

DT schema expects names of operating points tables to match certain
pattern:

  stih418-b2264.dtb: opp_table: $nodename:0: 'opp_table' does not match '^opp-table(-[a-z0-9]+)?$'

Link: https://lore.kernel.org/r/20230120072110.138627-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>