sched: Ignore offline CPUs in HMP migration & load stats

Previously, an offline CPU would always appear to have a zero load
and this would distort the offload functionality used for balancing
big and little domains.

Maintain a mask of online CPUs in each domain and use this instead.

Change-Id: I639b564b2f40cb659af8ceb8bd37f84b8a1fe323
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5e90359..0e2a546 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -888,6 +888,7 @@
 #ifdef CONFIG_SCHED_HMP
 struct hmp_domain {
 	struct cpumask cpus;
+	struct cpumask possible_cpus;
 	struct list_head hmp_domains;
 };
 #endif /* CONFIG_SCHED_HMP */