We only need register defines for the first two planes
on the first two pipes. Nuke everything else.

v2: Drop a few more that snuck through

Reviewed-by: Jani Nikula <jani.nikula@intel.com> #v1
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240513165842.15199-1-ville.syrjala@linux.intel.com