IB/mlx5: Avoid using user-index for SRQs

Normal SRQs, unlike XRC SRQs, don't have user-index, therefore
avoid verifying it and using it.

Fixes: cfb5e088 ('IB/mlx5: Add CQE version 1 support to user QPs and SRQs')
Signed-off-by: Majd Dibbiny <majd@mellanox.com>
Reviewed-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>