Add pageblock_align() macro and use it to simplify code.

Link: https://lkml.kernel.org/r/20220907060844.126891-2-wangkefeng.wang@huawei.comSigned-off-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: NMike Rapoport <rppt@linux.ibm.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>