drm/i915/rkl: Wa_1408330847 no longer applies to RKL

RKL doesn't have PSR2 support, so PSR2-related workarounds no longer
apply.

Bspec: 53273
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210717051426.4120328-7-matthew.d.roper@intel.com