VT-d: print_vtd_entries() should cope with superpages

VT-d: print_vtd_entries() should cope with superpages

Even if VT-d code alone (i.e. when not sharing tables with EPT) still
doesn't support superpages, this function - invoked upon DMA remapping
faults - needs to cope with such.

While at it also replace a few more plain numbers with suitable named
constants.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>