UPSTREAM: sched/fair: Use protect_slice() instead of direct comparison

Replace the test by the relevant protect_slice() function.

Bug: 438500731
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dhaval Giani (AMD) <dhaval@gianis.ca>
Link: https://lkml.kernel.org/r/20250708165630.1948751-2-vincent.guittot@linaro.org


(cherry picked from commit 9cdb4fe2)
Signed-off-by: Qais Yousef <qyousef@google.com>
Change-Id: Ied92fe9bc1eaf18683206f7b25d3a10ba73009dc