drm/i915/chv: Implement WaDisableShadowRegForCpd

This WA is avoid problem between shadow vs wake FIFO unload
problem during CPD/RC6 transactions on CHV.

v2: Define individual bits GTFIFOCTL (Ville)

v3: move WA to uncore_early_sanitize (ville)

Signed-off-by: Deepak S <deepak.s@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[Jani: fixed some whitespace issues while applying]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>