IB/hfi1: Fix ECN processing in prescan_rxq

When processing ECN via the prescan_rxq path, some fields in the packet
structure are passed uninitialized. This can potentially
cause NULL pointer exceptions during ECN handling.

Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Dasaratharaman Chandramouli <dasaratharaman.chandramouli@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>