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/[email protected]/

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

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Vlastimil Babka <[email protected]>
Reported-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Stephen Rothwell <[email protected]>

mm/slub.c

@@ -2913,11 +2913,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 
 load_freelist:
 
-#ifdef CONFIG_PREEMPT_RT
-	lockdep_assert_held(this_cpu_ptr(&s->cpu_slab->lock.lock));
-#else
 	lockdep_assert_held(this_cpu_ptr(&s->cpu_slab->lock));
-#endif
 
 	/*
 	 * freelist is pointing to the list of objects to be used.