This change makes it so that we map the entire page and just sync half of
it for the device at a time.  The advantage to this approach is that we can
avoid the locking on map/unmap seen in many IOMMU implementations.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>