net/mlx5: Enable QP number request when creating IPoIB underlay QP

If in the process of creating the underlay QP for an IPoIB interface
the user has set the address and specifically the 1st-3rd bytes
representing the QP number, use the requested QP number when creating
the underlay QP.

For a user to be able to request a QP number on QP creation, the MKEY_BY_NAME
NVCONFIG should be set. As mkey_by_name and qp_by_name are coupled in FW.
This requires driver to query the mkey_by_name max cap during initialization
and set the current cap if it was enabled in FW.

Signed-off-by: Michael Guralnik <michaelgur@mellanox.com>
Reviewed-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>