VT-d: protect against bogus information coming from BIOS

VT-d: protect against bogus information coming from BIOS

Add checks similar to those done by Linux: The DRHD address must not
be all zeros or all ones (Linux only checks for zero), and capabilities
as well as extended capabilities must not be all ones.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Ben Guthro <benjamin.guthro@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Tested-by: Ben Guthro <benjamin.guthro@citrix.com>
Acked by: Yang Zhang <yang.z.zhang@intel.com>
Acked-by: Xiantao Zhang <xiantao.zhang@intel.com>