cpufreq: Add stop CPU callback to cpufreq_driver interface

This callback allows the driver to do clean up before the CPU is
completely down and its state cannot be modified.  This is used
by the intel_pstate driver to reduce the requested P state prior to
the core going away.  This is required because the requested P state
of the offline core is used to select the package P state. This
effectively sets the floor package P state to the requested P state on
the offline core.

Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
[rjw: Minor modifications]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 3c56c47..3aa7a7a 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1337,6 +1337,8 @@
 				pr_debug("%s: policy Kobject moved to cpu: %d from: %d\n",
 					 __func__, new_cpu, cpu);
 		}
+	} else if (cpufreq_driver->stop_cpu && cpufreq_driver->setpolicy) {
+		cpufreq_driver->stop_cpu(policy);
 	}
 
 	return 0;