drm/i915: Include stepping information in device info dump

Dump the stepping information alongside all the other device
info. Might avoid some guesswork when reading logs.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230130181701.29977-1-ville.syrjala@linux.intel.com


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