FROMLIST: BACKPORT: mm/page_alloc: Split out buddy removal code from rmqueue into separate helper

This is a preparation page to allow the buddy removal code to be reused
in a later patch.

No functional change.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lore.kernel.org/all/20220420095906.27349-4-mgorman@techsingularity.net/



Conflicts:
        mm/page_alloc.c

1. Skipped changes in __rmqueue_pcplist which are not present in 5.10 kernel.
2. [1] introduced page allocation path a lot change to support cma first
   allocation policy so needed to adapt the change.

[1] ANDROID: cma: redirect page allocation to CMA

Bug: 230899966
Signed-off-by: Minchan Kim <minchan@google.com>
Change-Id: I4584fbfdebf2637534d6a68635a44a81a176c253