intel-iommu: Decode (and ignore) RHSA entries

I recently got a system where the DMAR table included a couple of RHSA
(remapping hardware static affinity) entries.  Rather than printing a
message about an "Unknown DMAR structure," it would probably be more
useful to dump the RHSA structure (as other DMAR structures are dumped).

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>