RDMA/uverbs: Fix an error flow in ib_uverbs_poll_cq

The new output_written block was wrongly placed before the ret=0, causing
the error code to be lost. uverbs_output_written is not expected to fail,
and even if it does fail it has no significant impact on the userspace
flow.
Reported-by: Bart Van Assche <bvanassche@acm.org>
Fixes: d6f4a21f ("RDMA/uverbs: Mark ioctl responses with UVERBS_ATTR_F_VALID_OUTPUT")
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>

drivers/infiniband/core/uverbs_cmd.c

@@ -1186,12 +1186,11 @@ static int ib_uverbs_poll_cq(struct uverbs_attr_bundle *attrs)
 		ret = -EFAULT;
 		goto out_put;
 	}
+	ret = 0;
 
 	if (uverbs_attr_is_valid(attrs, UVERBS_ATTR_CORE_OUT))
 		ret = uverbs_output_written(attrs, UVERBS_ATTR_CORE_OUT);
 
-	ret = 0;
-
 out_put:
 	uobj_put_obj_read(cq);
 	return ret;