RDMA/mlx5: Remove extraneous error check

Remove double error check from create user RQ error flow.

Fixes: 79b20a6c ("IB/mlx5: Add receive Work Queue verbs")
Signed-off-by: Gal Pressman <pressmangal@gmail.com>
Reviewed-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>