swap: clean-up #ifdef in page_mapping()

PageSwapCache() is always false when !CONFIG_SWAP, so compiler
properly discard related code. Therefore, we don't need #ifdef explicitly.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/util.c b/mm/util.c
index 7441c41..eaf63fc2 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -388,15 +388,12 @@
 	struct address_space *mapping = page->mapping;
 
 	VM_BUG_ON(PageSlab(page));
-#ifdef CONFIG_SWAP
 	if (unlikely(PageSwapCache(page))) {
 		swp_entry_t entry;
 
 		entry.val = page_private(page);
 		mapping = swap_address_space(entry);
-	} else
-#endif
-	if ((unsigned long)mapping & PAGE_MAPPING_ANON)
+	} else if ((unsigned long)mapping & PAGE_MAPPING_ANON)
 		mapping = NULL;
 	return mapping;
 }