IB/rdmavt: Macroize override checks during driver registration

Add a macro to cut down on writing the same lines over and over again for
what will be a large number of functions that will be supported.

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