direct-io: eliminate the offset argument to ->direct_IO

Including blkdev_direct_IO and dax_do_io.  It has to be ki_pos to actually
work, so eliminate the superflous argument.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index ac9225e..c37fb9c 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -245,9 +245,10 @@
  *
  */
 static ssize_t
-v9fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t pos)
+v9fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct file *file = iocb->ki_filp;
+	loff_t pos = iocb->ki_pos;
 	ssize_t n;
 	int err = 0;
 	if (iov_iter_rw(iter) == WRITE) {