staging/rdma/hfi1: add unique rnr timer

Add a new rnr timer to hfi1.

This allows for future optimizations having the
retry and rnr timers separate.

Reviewed-by: Jubin John <jubin.john@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>