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/splice.c b/fs/splice.c
index 153d4f3..51492f2 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -17,6 +17,7 @@
  * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
  *
  */
+#include <linux/bvec.h>
 #include <linux/fs.h>
 #include <linux/file.h>
 #include <linux/pagemap.h>