mm/memory-failure.c: remove useless "undef"s

Remove the useless #undef, since the corresponding #define has already
been removed.
Signed-off-by: Wang Xiaoqiang <wangxq10@lzu.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory-failure.c

@@ -826,8 +826,6 @@ static struct page_state {
 #undef lru
 #undef swapbacked
 #undef head
-#undef tail
-#undef compound
 #undef slab
 #undef reserved