ARM: dts: meson8: align OPP table names with DT schema

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

  meson8-minix-neo-x8.dtb: gpu-opp-table: $nodename:0: 'gpu-opp-table' does not match '^opp-table(-[a-z0-9]+)?$'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230120072108.138598-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>