mm/hugetlb: remove unused arch hook prepare/release_hugepage

With s390 dropping support for emulated hugepages, the last user of
arch_prepare_hugepage and arch_release_hugepage is gone.

Signed-off-by: Dominik Dingel <[e-mail]>
Acked-by: Martin Schwidefsky <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Christian Borntraeger <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/hugetlb.c

···
 		destroy_compound_gigantic_page(page, huge_page_order(h));
 		free_gigantic_page(page, huge_page_order(h));
 	} else {
-		arch_release_hugepage(page);
 		__free_pages(page, huge_page_order(h));
 	}
 }
···
 						__GFP_REPEAT|__GFP_NOWARN,
 		huge_page_order(h));
 	if (page) {
-		if (arch_prepare_hugepage(page)) {
-			__free_pages(page, huge_page_order(h));
-			return NULL;
-		}
 		prep_new_huge_page(h, page, nid);
 	}
 
···
 		page = alloc_pages_exact_node(nid,
 			htlb_alloc_mask(h)|__GFP_COMP|__GFP_THISNODE|
 			__GFP_REPEAT|__GFP_NOWARN, huge_page_order(h));
-
-	if (page && arch_prepare_hugepage(page)) {
-		__free_pages(page, huge_page_order(h));
-		page = NULL;
-	}
 
 	spin_lock(&hugetlb_lock);
 	if (page) {