MAINTAINERS: assign pagewalk.h to MEMORY MANAGEMENT

Patch series "kernel-doc and MAINTAINERS clean-up".

Roughly 900 warnings of about 21.000 kernel-doc warnings in the kernel
tree warn with 'cannot understand function prototype:', i.e., the
kernel-doc parser cannot parse the function's signature.  The majority,
about 600 cases of those, are just struct definitions following the
kernel-doc description.  Further, spot-check investigations suggest that
the authors of the specific kernel-doc descriptions simply were not
aware that the general format for a kernel-doc description for a
structure requires to prefix the struct name with the keyword 'struct',
as in 'struct struct_name - Brief description.'.  Details on kernel-doc
are at the Link below.

Without the struct keyword, kernel-doc does not check if the kernel-doc
description fits to the actual struct definition in the source code.
Fortunately, in roughly a quarter of these cases, the kernel-doc
description is actually complete wrt.  its corresponding struct
definition.  So, the trivial change adding the struct keyword will allow
us to keep the kernel-doc descriptions more consistent for future
changes, by checking for new kernel-doc warnings.

Also, some of the files in ./include/ are not assigned to a specific
MAINTAINERS section and hence have no dedicated maintainer.  So, if
needed, the files in ./include/ are also assigned to the fitting
MAINTAINERS section, as I need to identify whom to send the clean-up
patch anyway.

Here is the change from this kernel-doc janitorial work in the
./include/ directory for MEMORY MANAGEMENT.

This patch (of 2):

Commit a520110e

 ("mm: split out a new pagewalk.h header from mm.h")
adds a new file in ./include/linux, but misses to update MAINTAINERS
accordingly.  Hence,

  ./scripts/get_maintainers.pl include/linux/pagewalk.h

points only to lkml as general fallback for all files, whereas the
original include/linux/mm.h clearly marks this file part of MEMORY
MANAGEMENT.

Assign include/linux/pagewalk.h to MEMORY MANAGEMENT.

Link: https://lkml.kernel.org/r/20210322122542.15072-1-lukas.bulwahn@gmail.com
Link: https://lkml.kernel.org/r/20210322122542.15072-2-lukas.bulwahn@gmail.com
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Ralf Ramsauer <ralf.ramsauer@oth-regensburg.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>