Add some notes indicating which plane registers/bits are
valid for which platforms.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240516135622.3498-12-ville.syrjala@linux.intel.comAcked-by: Jani Nikula <jani.nikula@intel.com>