IB/hfi1: Use reference count wrapper for MRs

Some parts of the code don't use the standard driver
wrapper for memory region reference counters. Use the
standard driver wrapper throughout the code.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Sebastian Sanchez <sebastian.sanchez@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>