sched: do not allocate window cpu arrays separately

These are allocated extremely frequently.

Allocate them with CONFIG_NR_CPUS upon struct ravg's allocation.

This will break walt debug tracings.

Change-Id: I8f67bb00fb916e04bfc954d812a3b99a3a5495c2
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>