sched: entity load-tracking load_avg_ratio

This patch adds load_avg_ratio to each task. The load_avg_ratio is a
variant of load_avg_contrib which is not scaled by the task priority. It
is calculated like this:

runnable_avg_sum * NICE_0_LOAD / (runnable_avg_period + 1).

Signed-off-by: Morten Rasmussen <Morten.Rasmussen@arm.com>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index fe752ca..207054a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -931,6 +931,7 @@
 	u64 last_runnable_update;
 	s64 decay_count;
 	unsigned long load_avg_contrib;
+	unsigned long load_avg_ratio;
 	u32 usage_avg_sum;
 };