vfio/mlx5: error pointer dereference in error handling

This code frees the wrong "buf" variable and results in an error pointer
dereference.

Fixes: 34e2f271 ("vfio/mlx5: Introduce multiple loads")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/Y5IKia5SaiVxYmG5@kiliSigned-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/pci/mlx5/main.c

@@ -826,7 +826,7 @@ mlx5vf_pci_resume_device_data(struct mlx5vf_pci_core_device *mvdev)
 	spin_lock_init(&migf->list_lock);
 	return migf;
 out_buf:
-	mlx5vf_free_data_buffer(buf);
+	mlx5vf_free_data_buffer(migf->buf);
 out_pd:
 	mlx5vf_cmd_dealloc_pd(migf);
 out_free: