drm/i915: Constify remainder of the state checker

Mark the remaining crtc states used by the state checker as const.
There is no reason to ever mutate them here.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231004155607.7719-10-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>