IB/hfi1: Document phys port state bits not used in IB

A couple bits are used by OPA for link physical state that are not present
as part of InfiniBand. Add a short blurb what those states mean and removed
an unused state.

Cc: Leon Romanovsky <leon@kernel.org>
Reviewed-by: Todd Rimmer <todd.rimmer@intel.com>
Reviewed-by: Brent Rothermel <brent.r.rothermel@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>