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>

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"

fs/ntfs/mft.c

@@ -23,6 +23,7 @@
 #include <linux/buffer_head.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
+#include <linux/bio.h>
 
 #include "attrib.h"
 #include "aops.h"