remove call_{read,write}_iter() functions

These have no clear purpose.  This is effectively a revert of commit
bb7462b6fd64 ("vfs: use helpers for calling f_op->{read,write}_iter()").

The patch was created with the help of a coccinelle script.

Fixes: bb7462b6fd64 ("vfs: use helpers for calling f_op->{read,write}_iter()")
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/aio.c b/fs/aio.c
index 9cdaa2f..13ca81c 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1605,7 +1605,7 @@ static int aio_read(struct kiocb *req, const struct iocb *iocb,
 		return ret;
 	ret = rw_verify_area(READ, file, &req->ki_pos, iov_iter_count(&iter));
 	if (!ret)
-		aio_rw_done(req, call_read_iter(file, req, &iter));
+		aio_rw_done(req, file->f_op->read_iter(req, &iter));
 	kfree(iovec);
 	return ret;
 }
@@ -1636,7 +1636,7 @@ static int aio_write(struct kiocb *req, const struct iocb *iocb,
 		if (S_ISREG(file_inode(file)->i_mode))
 			kiocb_start_write(req);
 		req->ki_flags |= IOCB_WRITE;
-		aio_rw_done(req, call_write_iter(file, req, &iter));
+		aio_rw_done(req, file->f_op->write_iter(req, &iter));
 	}
 	kfree(iovec);
 	return ret;