vdpa/mlx5: Fix error return in map_direct_mr()

Fix to return the variable "err" from the error handling case instead
of "ret".

Fixes: 94abbcc ("vdpa/mlx5: Add shared memory registration code")
Signed-off-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Link: https://lore.kernel.org/r/20201026070637.164321-1-jingxiangfeng@huawei.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Eli Cohen <elic@nvidia.com>
Cc: stable@vger.kernel.org
Acked-by: Jason Wang <jasowang@redhat.com>

Author: hiss2018

drivers/vdpa/mlx5/core/mr.c

@@ -239,7 +239,6 @@ static int map_direct_mr(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_direct_mr
 	u64 paend;
 	struct scatterlist *sg;
 	struct device *dma = mvdev->mdev->device;
-	int ret;
 
 	for (map = vhost_iotlb_itree_first(iotlb, mr->start, mr->end - 1);
 	     map; map = vhost_iotlb_itree_next(map, start, mr->end - 1)) {
@@ -277,8 +276,8 @@ static int map_direct_mr(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_direct_mr
 done:
 	mr->log_size = log_entity_size;
 	mr->nsg = nsg;
-	ret = dma_map_sg_attrs(dma, mr->sg_head.sgl, mr->nsg, DMA_BIDIRECTIONAL, 0);
-	if (!ret)
+	err = dma_map_sg_attrs(dma, mr->sg_head.sgl, mr->nsg, DMA_BIDIRECTIONAL, 0);
+	if (!err)
 		goto err_map;
 
 	err = create_direct_mr(mvdev, mr);