vdpa/mlx5: Fix possible uninitialized return value

Initialize err local variable to return -EAGAIN if the asid cannot be
found thus avoiding returning uninitialized value.

Fixes: 8fcd20c3 ("vdpa/mlx5: Support different address spaces for control and data")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Eli Cohen <elic@nvidia.com>
Message-Id: <20220811134010.952291-1-elic@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/mlx5/net/mlx5_vnet.c

@@ -2659,7 +2659,7 @@ static int mlx5_vdpa_set_map(struct vdpa_device *vdev, unsigned int asid,
 {
 	struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
 	struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
-	int err;
+	int err = -EINVAL;
 
 	down_write(&ndev->reslock);
 	if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid) {