We have a per-CPU variable for managing which cluster a CPU belongs to.
Currently, physical_cluster is set for policy->cpu only which leads to
the following on some SoC's:

 - There are two clusters:
   - Cluster 0 has four ARM Cortex A7 CPUs (slower ones): 0,1,2,3
   - Cluster 1 has four ARM Cortex A15 CPUs (faster ones): 4,5,6,7
 - CPUs are booted in order 0,1..7 and so initially policy->cpu for A7 cluster
   would be 0 and for A15 cluster would be 4.
 - Now CPU4 (i.e. A15_0) is hotplugged out and so policy->cpu for A15 cluster
   becomes 5 (i.e. A15_1).
 - But physical cluster is only set for CPU0 and CPU4 in ARM big LITTLE driver
   and isn't updated.
 - Now freq change request comes for A15 cluster and we would try to update freq
   of physical_cluster of CPU5, i.e. A15_1. And it is currently set to zero
   (default value of uninitialized global variables).
 - And so we actually try to change freq of A7 cluster instead of A15.
 - This also results in kernel crash as sometimes we might request freq above
   A7's limit and CPU may behave badly..

Fix this by initializing physical_cluster for all CPUs of a policy.

Based on previous work by Xin Wang.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>