Revert "BACKPORT: mm: reclaim small amounts of memory when an external fragmentation event occurs"

This reverts commit 5cbbeadd.

Reason for revert: revert customized code
Bug: 140544941
Test: boot
Signed-off-by: Minchan Kim <minchan@google.com>
Signed-off-by: Martin Liu <liumartin@google.com>
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: I65735f27f6a44a112957bcec07e2f63f2d8ccff6