sched/walt: factor out WALT from HMP scheduler

At present, hmp.c contains HMP task placement logic as well as WALT.
Factor out WALT logic into a separate file walt.c so EAS can use WALT as
CPU load tracking and frequency guidance algorithm.

Also set sched_io_is_busy = 1 by default.

Change-Id: I96c3fd7d637b9bfa283083a1a6ff6d5dd261e0fb
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 5cc0a36..c573113 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1506,7 +1506,7 @@
 
 #endif	/* CONFIG_SMP */
 
-#ifdef CONFIG_SCHED_HMP
+#ifdef CONFIG_SCHED_WALT
 
 static int sched_init_task_load_show(struct seq_file *m, void *v)
 {
@@ -3062,7 +3062,7 @@
 #ifdef CONFIG_SMP
 	REG("sched_wake_up_idle",      S_IRUGO|S_IWUSR, proc_pid_sched_wake_up_idle_operations),
 #endif
-#ifdef CONFIG_SCHED_HMP
+#ifdef CONFIG_SCHED_WALT
 	REG("sched_init_task_load",      S_IRUGO|S_IWUSR, proc_pid_sched_init_task_load_operations),
 	REG("sched_group_id",      S_IRUGO|S_IWUGO, proc_pid_sched_group_id_operations),
 #endif