IB/hfi1: Do not allocate PIO send contexts for VNIC

OPA VNIC does not use PIO contexts and instead only uses SDMA
engines. Do not allocate PIO contexts for VNIC ports.

Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>