This patch introduces amdgpu_drm_plane_state
structure, which subclasses drm_plane_state and
holds data suitable for configuring hardware.

It switches reset(), atomic_duplicate_state()
& atomic_destroy_state() functions to new internal
implementation, earlier they were pointing to
drm core functions.

TESTS(On Chromium OS on Stoney Only)
* Builds without compilation errors.
* 'plane_test' passes for XR24 format
  based Overlay plane.
* Chromium OS ui comes up.
Signed-off-by: Shirish S <shirish.s@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>