drm/i915/dg2: Drop pre-production GT workarounds

DG2 first production steppings were C0 (for DG2-G10), B1 (for DG2-G11),
and A1 (for DG2-G12).  Several workarounds that apply onto to
pre-production hardware can be dropped.  Furthermore, several
workarounds that apply to all production steppings can have their
conditions simplified to no longer check the GT stepping.

v2:
 - Keep Wa_16011777198 in place for now; it will be removed separately
   in a follow-up patch to keep review easier.

Bspec: 44477
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Matt Atwood <matthew.s.atwood@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230816214201.534095-10-matthew.d.roper@intel.com