mm/page_alloc: fix obsolete comment in deferred_pfn_valid()

There are no architectures that can have holes in the memory map within a
pageblock since commit 859a85dd ("mm: remove pfn_valid_within() and
CONFIG_HOLES_IN_ZONE").  Update the corresponding comment.

Link: https://lkml.kernel.org/r/20220916072257.9639-17-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_alloc.c

@@ -1929,11 +1929,7 @@ static inline void __init pgdat_init_report_one_done(void)
 /*
  * Returns true if page needs to be initialized or freed to buddy allocator.
  *
- * First we check if pfn is valid on architectures where it is possible to have
- * holes within pageblock_nr_pages. On systems where it is not possible, this
- * function is optimized out.
- *
- * Then, we check if a current large page is valid by only checking the validity
+ * We check if a current large page is valid by only checking the validity
  * of the head pfn.
  */
 static inline bool __init deferred_pfn_valid(unsigned long pfn)