mm/page_alloc: reword the comment of buddy_merge_likely()

For page with order O, we are checking its order (O + 1)'s buddy.  If it
is free, we would like to put it to the tail and expect it would be merged
to a page with order (O + 2).

Reword the comment to reflect it.

Link: https://lkml.kernel.org/r/20240619010612.20740-4-richard.weiyang@gmail.comSigned-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_alloc.c

@@ -712,12 +712,12 @@ static inline struct page *get_page_from_free_area(struct free_area *area,
 }
 
 /*
- * If this is not the largest possible page, check if the buddy
- * of the next-highest order is free. If it is, it's possible
+ * If this is less than the 2nd largest possible page, check if the buddy
+ * of the next-higher order is free. If it is, it's possible
  * that pages are being freed that will coalesce soon. In case,
  * that is happening, add the free page to the tail of the list
  * so it's less likely to be used soon and more likely to be merged
- * as a higher order page
+ * as a 2-level higher order page
  */
 static inline bool
 buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,