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/fs/udf/inode.c b/fs/udf/inode.c
index a685aea..4f178c8 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -215,8 +215,7 @@
 	return ret;
 }
 
-static ssize_t udf_direct_IO(int rw, struct kiocb *iocb,
-			     struct iov_iter *iter,
+static ssize_t udf_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 			     loff_t offset)
 {
 	struct file *file = iocb->ki_filp;