docs: put atomic*.txt and memory-barriers.txt into the core-api book

These files describe part of the core API, but have never been converted to
RST due to ... let's say local oppposition.  So, create a set of
special-purpose wrappers to ..include these files into a separate page so
that they can be a part of the htmldocs build.  Then link them into the
core-api manual and remove them from the "staging" dumping ground.
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Reviewed-by: David Vernet <void@manifault.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20220927160559.97154-7-corbet@lwn.netSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/core-api/index.rst

@@ -45,6 +45,8 @@ Library functionality that is used throughout the kernel.
    this_cpu_ops
    timekeeping
    errseq
+   wrappers/atomic_t
+   wrappers/atomic_bitops
 
 Low level entry and exit
 ========================
@@ -68,6 +70,7 @@ Documentation/locking/index.rst for more related documentation.
    local_ops
    padata
    ../RCU/index
+   wrappers/memory-barriers.rst
 
 Low-level hardware management
 =============================

Documentation/core-api/wrappers/atomic_bitops.rst

+.. SPDX-License-Identifier: GPL-2.0
+   This is a simple wrapper to bring atomic_bitops.txt into the RST world
+   until such a time as that file can be converted directly.
+
+=============
+Atomic bitops
+=============
+
+.. raw:: latex
+
+    \footnotesize
+
+.. include:: ../../atomic_bitops.txt
+   :literal:
+
+.. raw:: latex
+
+    \normalsize

Documentation/core-api/wrappers/atomic_t.rst

+.. SPDX-License-Identifier: GPL-2.0
+   This is a simple wrapper to bring atomic_t.txt into the RST world
+   until such a time as that file can be converted directly.
+
+============
+Atomic types
+============
+
+.. raw:: latex
+
+    \footnotesize
+
+.. include:: ../../atomic_t.txt
+   :literal:
+
+.. raw:: latex
+
+    \normalsize
+

Documentation/core-api/wrappers/memory-barriers.rst

+.. SPDX-License-Identifier: GPL-2.0
+   This is a simple wrapper to bring memory-barriers.txt into the RST world
+   until such a time as that file can be converted directly.
+
+============================
+Linux kernel memory barriers
+============================
+
+.. raw:: latex
+
+    \footnotesize
+
+.. include:: ../../memory-barriers.txt
+   :literal:
+
+.. raw:: latex
+
+    \normalsize

Documentation/staging/index.rst

@@ -14,45 +14,3 @@ Unsorted Documentation
    static-keys
    tee
    xz
-
-Atomic Types
-============
-
-.. raw:: latex
-
-    \footnotesize
-
-.. include:: ../atomic_t.txt
-   :literal:
-
-.. raw:: latex
-
-    \normalsize
-
-Atomic bitops
-=============
-
-.. raw:: latex
-
-    \footnotesize
-
-.. include:: ../atomic_bitops.txt
-   :literal:
-
-.. raw:: latex
-
-    \normalsize
-
-Memory Barriers
-===============
-
-.. raw:: latex
-
-    \footnotesize
-
-.. include:: ../memory-barriers.txt
-   :literal:
-
-.. raw:: latex
-
-    \normalsize