mm: only include blk_types in swap.h if CONFIG_SWAP is enabled

It's only needed for the CONFIG_SWAP-only use of bio_end_io_t.

Because CONFIG_SWAP implies CONFIG_BLOCK this will allow to drop some
ifdefs in blk_types.h.

Instead we'll need to add a few explicit includes that were implicit
before, though.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index fe251f1..d0cf6fe 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -29,6 +29,7 @@
 #include <linux/buffer_head.h>
 #include <linux/writeback.h>
 #include <linux/bit_spinlock.h>
+#include <linux/bio.h>
 
 #include "aops.h"
 #include "attrib.h"