cpufreq: dt-platdev: Blocklist Allwinner H616/618 SoCs

The AllWinner H616 SoC will use the (extended) H6 OPP driver, so add
them to the cpufreq-dt blocklist, to not create the device twice.
This also affects the closely related sibling SoCs H618 and H700.

Signed-off-by: Martin Botka <martin.botka@somainline.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>