mm, slab: simplify lockdep_assert_held in lockdep_assert_held()

mm, slab: simplify lockdep_assert_held in lockdep_assert_held()

Sebastian reports [1] that the special version of lockdep_assert_held() for a
local lock with PREEMPT_RT is no longer necessary, and we can simplify.

[1] https://lore.kernel.org/linux-mm/20210817153937.hxnuh7mqp6vuiyws@linutronix.de/

This is a fixup for mmotm patch
mm-slub-convert-kmem_cpu_slab-protection-to-local_lock.patch

Link: https://lkml.kernel.org/r/7e9ccf34-57d1-786b-2dfd-3b9ba78e1b32@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>