percpu: Replace smp_read_barrier_depends() with lockless_dereference()

Recently lockless_dereference() was added which can be used in place of
hard-coding smp_read_barrier_depends(). The following PATCH makes the change.
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

include/linux/percpu-refcount.h

@@ -128,10 +128,8 @@ static inline void percpu_ref_kill(struct percpu_ref *ref)
 static inline bool __ref_is_percpu(struct percpu_ref *ref,
 					  unsigned long __percpu **percpu_countp)
 {
-	unsigned long percpu_ptr = ACCESS_ONCE(ref->percpu_count_ptr);
-
 	/* paired with smp_store_release() in percpu_ref_reinit() */
-	smp_read_barrier_depends();
+	unsigned long percpu_ptr = lockless_dereference(ref->percpu_count_ptr);
 
 	if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC))
 		return false;