Revert "workqueue: RCU protect wq->dfl_pwq and implement accessors for it"

Revert "workqueue: RCU protect wq->dfl_pwq and implement accessors for it"

This reverts commit bd31fb926dfa02d2ccfb4b79389168b1d16f36b1 which is
commit 9f66cff212bb3c1cd25996aaa0dfd0c9e9d8baab upstream.

The workqueue patches backported to 6.6.y caused some reported
regressions, so revert them for now.

Reported-by: Thorsten Leemhuis <regressions@leemhuis.info>
Cc: Tejun Heo <tj@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Audra Mitchell <audra@redhat.com>
Link: https://lore.kernel.org/all/ce4c2f67-c298-48a0-87a3-f933d646c73b@leemhuis.info/
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>