Since commit 44042b44 ("mm/page_alloc: allow high-order pages to be
stored on the per-cpu lists"), the per-cpu page allocators (PCP) is not
only for order-0 pages.  Update the comments.

Link: https://lkml.kernel.org/r/20220918025640.208586-1-ran.xiaokai@zte.com.cnSigned-off-by: NRan Xiaokai <ran.xiaokai@zte.com.cn>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>