Revert "FROMLIST: sched: Fix use-after-free bug in dup_user_cpus_ptr()"

This reverts commit 28f65c4a.

This patch gets in the way of reverting the sched_setaffinity() changes
which were backported from 6.2-rc. Revert it for now -- we'll bring it
back later using the commit from -stable.

Signed-off-by: Will Deacon <willdeacon@google.com>
Bug: 263926519
Bug: 264940090
Bug: 269965243
Change-Id: Iec078ad43db28d7be8d4eb49368f5c40f0ff4b7e
(cherry picked from commit 92bd55bc)