mm/dynamic_pool: add interface to configure the count of hugepages

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8S9BY


CVE: NA

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Add two interfaces to configure the count of 1G/2M hugepages.
	`echo <number> > dhugetlb.1G.reserved_page`
	`echo <number> > dhugetlb.2M.reserved_page`

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