IB/hfi1: Use VL15 for SM packets

Subnet Management Packets (SMP) should exclusively use VL15 and their SL
is ignored (IBTA v1.3, Section 3.5.8.2). Therefore, when an SMP is posted,
the SL in the address handle can be set to 0 by a user
application. Consequently, when an address handle is created by the IB
core, some fields in struct rvt_ah may not be set correctly by using the
SL2SC and SC2VL tables at the time. Subsequently, when the request is post
sent, the incoming swqe may fail the validation check, resulting in the
rejection of the send request.

This patch fixes the problem by using VL15 for any validation, ignoring
the SL in the address handle.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>