drm/xe/display: fix compat IS_DISPLAY_STEP() range end

drm/xe/display: fix compat IS_DISPLAY_STEP() range end

It's supposed to be an open range at the end like in i915. Fingers
crossed that nobody relies on this definition.

Fixes: 44e694958b95 ("drm/xe/display: Implement display support")
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
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/fe8743770694e429f6902491cdb306c97bdf701a.1724180287.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>