IB/hfi1: Remove unnecessary fecn and becn fields

packet->fecn and packet->becn are calculated in the hot path
and are never used. Remove these fields as they show to be
costly in a profile. Also, remove initialization for
becn and fecn in process_ecn() as they're unconditionally
assigned in the function and ensure fecn and becn variables
use a boolean type.

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: Jason Gunthorpe <jgg@mellanox.com>