PM: EM: Slightly reduce em_check_capacity_update() overhead

Every iteration of the loop over all possible CPUs in
em_check_capacity_update() causes get_cpu_device() to be called twice
for the same CPU, once indirectly via em_cpu_get() and once directly.

Get rid of the indirect get_cpu_device() call by moving the direct
invocation of it earlier and using em_pd_get() instead of em_cpu_get()
to get a pd pointer for the dev one returned by it.

This also exposes the fact that dev is needed to get a pd, so the code
becomes somewhat easier to follow after it.

No functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://patch.msgid.link/1925950.tdWV9SEqCh@rjwysocki.net

Author: rafaeljw

kernel/power/energy_model.c

@@ -774,7 +774,8 @@ static void em_check_capacity_update(void)
 		}
 		cpufreq_cpu_put(policy);
 
-		pd = em_cpu_get(cpu);
+		dev = get_cpu_device(cpu);
+		pd = em_pd_get(dev);
 		if (!pd || em_is_artificial(pd))
 			continue;
 
@@ -798,7 +799,6 @@ static void em_check_capacity_update(void)
 		pr_debug("updating cpu%d cpu_cap=%lu old capacity=%lu\n",
 			 cpu, cpu_capacity, em_max_perf);
 
-		dev = get_cpu_device(cpu);
 		em_adjust_new_capacity(dev, pd);
 	}