cpufreq: dt: Identify cpu-sharing for platforms without operating-points-v2

Existing platforms, which do not support operating-points-v2, can
explicitly tell the opp core that some of the CPUs share opp tables,
with help of dev_pm_opp_set_sharing_cpus().

For such platforms, explicitly ask the opp core to provide list of CPUs
sharing the opp table with current cpu device, before falling back to
platform data.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>