drm/i915: Remove early pre-production RPS workarounds for BXT

Remove WaGsvDisableTurbo and WaRsUseTimeoutMode as these were only for
pre-production Broxton devices, and this code is now defunct.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>