mm: kmsan: use helper macros PAGE_ALIGN and PAGE_ALIGN_DOWN

Use helper macros PAGE_ALIGN and PAGE_ALIGN_DOWN to improve code
readability.  No functional modification involved.

Link: https://lkml.kernel.org/r/20230727011612.2721843-4-zhangpeng362@huawei.comSigned-off-by: ZhangPeng <zhangpeng362@huawei.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Marco Elver <elver@google.com>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/kmsan/shadow.c

@@ -281,8 +281,8 @@ void __init kmsan_init_alloc_meta_for_range(void *start, void *end)
 	struct page *page;
 	u64 size;
 
-	start = (void *)ALIGN_DOWN((u64)start, PAGE_SIZE);
-	size = ALIGN((u64)end - (u64)start, PAGE_SIZE);
+	start = (void *)PAGE_ALIGN_DOWN((u64)start);
+	size = PAGE_ALIGN((u64)end - (u64)start);
 	shadow = memblock_alloc(size, PAGE_SIZE);
 	origin = memblock_alloc(size, PAGE_SIZE);
 	for (u64 addr = 0; addr < size; addr += PAGE_SIZE) {