This finishes the objective in the last patch which was to actually deal
with physical addresses, and not the PTEs.
GEN6+ Provided support for physical addresses above 4GB. I'm not
actually sure what Ironlake supported, and don't feel like firing up the
timemachine.
v2: Add support for gen4, gen5, and haswell.
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>