RDS: IB: drop discontinued IB CQ_VECTOR support

RDS: IB: drop discontinued IB CQ_VECTOR support

IB_CQ_VECTOR_LEAST_ATTACHED was OFED 1.5 feature which later Mellanox
dropped. As per them 'least attached' was not a way to distribute the load
and that actually fools the user to think it does so. The fact that some
cpu had 'least amount of attached cqs' has nothing to do with this cpu
actual load. This is why the feature never made to upstream.

On UEK4, the code is already under #if 0 because feature isn't
available. Time to clean up the dead code considering its already
dropped from upstream as well as OFED2.0+ onwards.

Orabug: 23027670

Tested-by: Michael Nowak <michael.nowak@oracle.com>
Tested-by: Rose Wang <rose.wang@oracle.com>
Tested-by: Rafael Alejandro Peralez <rafael.peralez@oracle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>