sched/psi: Rearrange polling code in preparation

[ Upstream commit 7fab21fa ]

Move a few functions up in the file to avoid forward declaration needed
in the patch implementing unprivileged PSI triggers.

Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20230330105418.77061-2-cerasuolodomenico@gmail.com


Stable-dep-of: aff03707 ("sched/psi: use kernfs polling functions for PSI trigger polling")
Signed-off-by: Sasha Levin <sashal@kernel.org>