mm/page_alloc.c: add sysctl to revise the batch and high of percpu pageset

hulk inclusion
category: performance
bugzilla: 187468, https://gitee.com/openeuler/kernel/issues/I61HVC



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Patch d8a759b5 ("mm, page_alloc: double zone's batchsize") change the
default batchsize. For some machines with large memory, the value seems to
be too large. Although percpu_pagelist_fraction can be used to revise the
batchsize but needs to be adjusted based on managed memory.
So add a new sysctl percpu_max_batchsize to revise the batchsize to adapt
different scenarios.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>