Docs/admin-guide/mm/numaperf: increase depth of subsections

Each section of numaperf.rst has zero depth, and therefore be exposed to
the index of admin-guide/mm.  Especially 'See Also' section on the index
makes the document weird.  Hide the sections from the index by giving the
document a title and increasing the depth of each section.

[sj@kernel.org: change title to fix duplicate label warning]
  Link: https://lkml.kernel.org/r/20230106194927.152663-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20230103180754.129637-6-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/admin-guide/mm/numaperf.rst

 .. _numaperf:
 
-=============
+=======================
+NUMA Memory Performance
+=======================
+
 NUMA Locality
 =============
 
@@ -61,7 +64,6 @@ that are CPUs and hence suitable for generic task scheduling, and
 IO initiators such as GPUs and NICs.  Unlike access class 0, only
 nodes containing CPUs are considered.
 
-================
 NUMA Performance
 ================
 
@@ -96,7 +98,6 @@ for the platform.
 Access class 1 takes the same form but only includes values for CPU to
 memory activity.
 
-==========
 NUMA Cache
 ==========
 
@@ -170,7 +171,6 @@ The "size" is the number of bytes provided by this cache level.
 The "write_policy" will be 0 for write-back, and non-zero for
 write-through caching.
 
-========
 See Also
 ========