staging/rdma/hfi1: add cq head and tail information to qpstats

This enables debugging issues related to cq event signalling mechanism

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Vennila Megavannan <vennila.megavannan@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>