pipe: fix failure to return error code on ->confirm()

The arguments were transposed, we want to assign the error code to
'ret', which is being returned.

Signed-off-by: Nicolas Kaiser <nikai@nikai.net>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/fs/pipe.c b/fs/pipe.c
index 279eef9..37eb1eb 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -382,7 +382,7 @@
 			error = ops->confirm(pipe, buf);
 			if (error) {
 				if (!ret)
-					error = ret;
+					ret = error;
 				break;
 			}