arm64: dts: rockchip: align rk3399 DMC OPP table with bindings

[ Upstream commit b67b0973

 ]

Bindings expect certain pattern for OPP table node name and underscores
are not allowed:

  rk3399-rock-pi-4a-plus.dtb: dmc_opp_table: $nodename:0: 'dmc_opp_table' does not match '^opp-table(-[a-z0-9]+)?$'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230119124631.91080-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>