linux-imx

drm/i915/gvt: Refine ggtt and ppgtt root entry ops

Separate ggtt and ppgtt since they are different. A little more code but
straightforward.

And move these helpers to gtt.c since that is the only client.

Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>