drm/i915/display: switch to display detected steppings

drm/i915/display: switch to display detected steppings

Move the stepping related macros over to display. We can proceed to
remove the compat macros from xe.

Note: Looks like we've failed to actually initialize the display
stepping for GMD ID based platforms in the xe driver. It does get set in
display runtime info, but until now the compat macro used
xe->info.step.display which was not set for GMD ID.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/ce8bb94e1a801d3c345f1810837bdd1964c3af75.1724180287.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>