UPSTREAM: mm/page_alloc: add some detailed comments in can_steal_fallback

mm/page_alloc: add some detailed comments in can_steal_fallback

[akpm@linux-foundation.org: tweak grammar, fit to 80 cols]
Link: https://lkml.kernel.org/r/20240920122030.159751-1-gxxa03070307@gmail.com


Signed-off-by: gaoxiang17 <gaoxiang17@xiaomi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Bug: 420836317
Bug: 429525621
(cherry picked from commit 6025ea5a)
Change-Id: Ib4a77bf96edeba6ce2c6627c99aacaf148b07d92
Signed-off-by: yipeng xiang <yipengxiang@honor.corp-partner.google.com>