PM / Hibernate: Correct additional pages number calculation

The struct bm_block is allocated by chain_alloc(),
so it'd better counting it in LINKED_PAGE_DATA_SIZE.

Signed-off-by: Namhyung Kim <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

kernel/power/snapshot.c

···
 	unsigned int res;
 
 	res = DIV_ROUND_UP(zone->spanned_pages, BM_BITS_PER_BLOCK);
-	res += DIV_ROUND_UP(res * sizeof(struct bm_block), PAGE_SIZE);
+	res += DIV_ROUND_UP(res * sizeof(struct bm_block),
+			    LINKED_PAGE_DATA_SIZE);
 	return 2 * res;
 }