If queued invalidation interface is available and enabled, queued invalidation
interface will be used instead of the register based interface.

According to Vt-d2 specification, when queued invalidation is enabled,
invalidation command submit works only through invalidation queue and not
through the command registers interface.
Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>