cpufreq: dt-platdev: allow RK3399 to have separate tunables per cluster

RK3899 has one cluster with 4 small cores, and another one with 2 big
cores, with cores in different clusters having different OPPs and thus
needing separate set of tunables. Let's enable this via
"have_governor_per_policy" platform data.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>