Use helper macro SZ_1K, SZ_1M and SZ_1G to do the size conversion. Minor
readability improvement.

Link: https://lkml.kernel.org/r/20220729080106.12752-3-linmiaohe@huawei.comSigned-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Reviewed-by: NMina Almasry <almasrymina@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>