UPSTREAM: sched/headers: Move loadavg related definitions from <linux/sched.h>...

UPSTREAM: sched/headers: Move loadavg related definitions from <linux/sched.h> to <linux/sched/loadavg.h>

Move these bits to <linux/sched/loadavg.h>, to reduce the size and
complexity of <linux/sched.h>.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

(cherry picked from commit dea38c74cb9205341f52b8d8ae18f61247a43ea8)

Bug: 111308141
Test: modified lmkd to use PSI and tested using lmkd_unit_test

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: If827d04c87fa957f684a7a879766d9c910b1da90