mm/hugetlb: remove hugetlb_set_page_subpool()

All users have been converted to hugetlb_set_folio_subpool() so we can
safely remove this function.

Link: https://lkml.kernel.org/r/20230623054948.280627-1-sidhartha.kumar@oracle.com
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Tarun Sahu <tsahu@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Sidhartha Kumar

include/linux/hugetlb.h

@@ -761,12 +761,6 @@ static inline void hugetlb_set_folio_subpool(struct folio *folio,
 	folio->_hugetlb_subpool = subpool;
 }
 
-static inline void hugetlb_set_page_subpool(struct page *hpage,
-					struct hugepage_subpool *subpool)
-{
-	hugetlb_set_folio_subpool(page_folio(hpage), subpool);
-}
-
 static inline struct hstate *hstate_file(struct file *f)
 {
 	return hstate_inode(file_inode(f));