cppc_cpufreq: use policy->cpu as driver of frequency setting

Considering only the currently supported coordination types (ANY, HW,
NONE), this change only makes a difference for the ANY type, when
policy->cpu is hotplugged out. In that case the new policy->cpu will
be different from ((struct cppc_cpudata *)policy->driver_data)->cpu.

While in this case the controls of *ANY* CPU could be used to drive
frequency changes, it's more consistent to use policy->cpu as the
leading CPU, as used in all other cppc_cpufreq functions. Additionally,
the debug prints in cppc_set_perf() would no longer create confusion
when referring to a CPU that is hotplugged out.

Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Mian Yousaf Kaukab <ykaukab@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>