drm/i915: Add missing invalidate to g4x wm readout

Let's not forget to mark the unused watermark levels as invalid
after the readout. The vlv/chv codepath has this but the g4x
didn't for some reason.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220622155452.32587-6-ville.syrjala@linux.intel.com
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -3846,6 +3846,8 @@ void g4x_wm_get_hw_state(struct drm_i915_private *dev_priv)
 					     plane_id, USHRT_MAX);
 		g4x_raw_fbc_wm_set(crtc_state, level, USHRT_MAX);
 
+		g4x_invalidate_wms(crtc, active, level);
+
 		crtc_state->wm.g4x.optimal = *active;
 		crtc_state->wm.g4x.intermediate = *active;