rds: ib: Implement proper cm_id compare

rds: ib: Implement proper cm_id compare

RDS attempts to establish if two rdma_cm_ids actually are the
same. This was implemented by comparing their addresses. But, an
rdma_cm_id may be destroyed and allocated again. Thus, a *new* id, but
the address could still be the same as the *old* one.

Solved by using an idr id as the cm_id's context. Added helper
functions to create and destroy rdma_cm_ids and comparing the
rdma_cm_ids.

Orabug: 29391909

Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Tested-by: Rosa Lopez <rosa.lopez@oracle.com>
Reviewed-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>