Broxton has the same panel fitter registers as Skylake.

v2:
- add MISSING_CASE for future platforms (daniel)
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NSagar Kamble <sagar.a.kamble@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>