Group the pre-skl primary plane register definitions
sensible, and toss in a few comments to indicate which
platforms have what.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240516135622.3498-11-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>