IB/hfi1: Look up ibport using a pointer in receive path

In the receive path, hfi1_ibport is looked up by indexing into an
array. A profile shows this to be expensive. The receive context
data has a pointer to the ibport data, use that pointer instead.

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>