memory-barriers.txt: Fix broken link to atomic_ops.txt

Few obsolete links to atomic_ops.txt exist in memory-barriers.txt though
the file has moved to core-api/atomic_ops.rst.  This commit fixes the
obsolete links.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index f1c9eaa..3ed0d8b 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1876,8 +1876,8 @@
      This makes sure that the death mark on the object is perceived to be set
      *before* the reference counter is decremented.
 
-     See Documentation/atomic_ops.txt for more information.  See the "Atomic
-     operations" subsection for information on where to use these.
+     See Documentation/core-api/atomic_ops.rst for more information.  See the
+     "Atomic operations" subsection for information on where to use these.
 
 
  (*) lockless_dereference();
@@ -2584,7 +2584,7 @@
 barriers, and so barrier instructions are superfluous in conjunction with them,
 and in such cases the special barrier primitives will be no-ops.
 
-See Documentation/atomic_ops.txt for more information.
+See Documentation/core-api/atomic_ops.rst for more information.
 
 
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