direct_IO: remove rw from a_ops->direct_IO()

Now that no one is using rw, remove it completely.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index b01ccf3..3d1b0d2 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -447,7 +447,7 @@
 /*
  * linux/fs/nfs/direct.c
  */
-extern ssize_t nfs_direct_IO(int, struct kiocb *, struct iov_iter *, loff_t);
+extern ssize_t nfs_direct_IO(struct kiocb *, struct iov_iter *, loff_t);
 extern ssize_t nfs_file_direct_read(struct kiocb *iocb,
 			struct iov_iter *iter,
 			loff_t pos);