UPSTREAM: sched/headers: Remove <linux/sched.h> from <linux/sched/loadavg.h>

The <linux/sched/loadavg.h> file is a self-contained header and users of
it either don't need <linux/sched.h> - or have already included it.

This reduces the size of the header dependency graph.

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 5a2d6880f461faa416c0d329d46a128cf342c1eb)

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

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: I45ce1853bddcc5bf24643a8e6bdd420dbd6f2083