Documentation/vm: move user guides to admin-guide/mm/

Most memory management user guide documents are in 'admin-guide/mm/',
but two of those are in 'vm/'.  This moves the two docs into
'admin-guide/mm' for easier documents finding.

Link: https://lkml.kernel.org/r/20210917123958.3819-2-sj@kernel.org
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/admin-guide/mm/index.rst

@@ -37,5 +37,7 @@ the Linux memory management.
    numaperf
    pagemap
    soft-dirty
+   swap_numa
    transhuge
    userfaultfd
+   zswap

Documentation/vm/index.rst

@@ -3,27 +3,11 @@ Linux Memory Management Documentation
 =====================================
 
 This is a collection of documents about the Linux memory management (mm)
-subsystem.  If you are looking for advice on simply allocating memory,
-see the :ref:`memory_allocation`.
-
-User guides for MM features
-===========================
-
-The following documents provide guides for controlling and tuning
-various features of the Linux memory management
-
-.. toctree::
-   :maxdepth: 1
-
-   swap_numa
-   zswap
-
-Kernel developers MM documentation
-==================================
-
-The below documents describe MM internals with different level of
-details ranging from notes and mailing list responses to elaborate
-descriptions of data structures and algorithms.
+subsystem internals with different level of details ranging from notes and
+mailing list responses for elaborating descriptions of data structures and
+algorithms.  If you are looking for advice on simply allocating memory, see the
+:ref:`memory_allocation`.  For controlling and tuning guides, see the
+:doc:`admin guide <../admin-guide/mm/index>`.
 
 .. toctree::
    :maxdepth: 1