cpufreq: sun50i: fix memory leak in dt_has_supported_hw()

The for_each_child_of_node() loop does not decrement the child node
refcount before the break instruction, even though the node is no
longer required.

This can be avoided with the new for_each_child_of_node_scoped() macro
that removes the need for any of_node_put().

Fixes: fa5aec95

 ("cpufreq: sun50i: Add support for opp_supported_hw")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>