rcu: merge fix for Convert ACCESS_ONCE() to READ_ONCE() and WRITE_ONCE()

This mirrors the change introduced by 7d0ae8086b8 of same title
in Linus' tree; it's not obvious as a merge resolution since we moved
the function.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

include/linux/compiler.h

@@ -467,7 +467,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
  */
 #define lockless_dereference(p) \
 ({ \
-	typeof(p) _________p1 = ACCESS_ONCE(p); \
+	typeof(p) _________p1 = READ_ONCE(p); \
 	smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
 	(_________p1); \
 })