drm/i915/icl: Drop workarounds that only apply to pre-production steppings

We're past the point at which we usually drop workarounds that were
never needed on production hardware.  The driver will already print an
error and apply taint if loaded on pre-production hardware.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210713193635.3390052-13-matthew.d.roper@intel.com