block: don't include io.h from bio.h

Now that we don't need an override for BIOVEC_PHYS_MERGEABLE there is
no need to drag this header in.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/bio.h

@@ -24,9 +24,6 @@
 #include <linux/bug.h>
 
 #ifdef CONFIG_BLOCK
-
-#include <asm/io.h>
-
 /* struct bio, bio_vec and BIO_* flags are defined in blk_types.h */
 #include <linux/blk_types.h>