UPSTREAM: mm: multi-gen LRU: improve walk_pmd_range()

Improve readability of walk_pmd_range() and walk_pmd_range_locked().

Link: https://lkml.kernel.org/r/20230118001827.1040870-7-talumbau@google.com


Change-Id: Ia084fbf53fe989673b7804ca8ca520af12d7d52a
Signed-off-by: T.J. Alumbaugh <talumbau@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit b5ff4133)
Bug: 274865848
Signed-off-by: T.J. Mercier <tjmercier@google.com>