IB/rdmavt: Initialize and teardown of qpn table

Add table init as well as teardown for handling qpn maps. Drivers can still
provide this functionality by setting the QP_INIT_DRIVER bit.

Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>