cpufreq: SPEAr: Notify all policy->cpus of frequency change

SPEAr cpufreq driver supports dual core Cortex-A9 SoC's, where cpus share policy
structure. Whenever we update frequency of a cpu, we must notify all
policy->cpus.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>