drm/i915: Fix the state checker for ICL Y planes

The plane used to scan out NV12 luma on ICL is logically
off but actually on. Fix the state checker to account for this.

Cc: Imre Deak <imre.deak@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109457Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190304131217.4338-1-ville.syrjala@linux.intel.comReviewed-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -12589,7 +12589,8 @@ intel_verify_planes(struct intel_atomic_state *state)
 
 	for_each_new_intel_plane_in_state(state, plane,
 					  plane_state, i)
-		assert_plane(plane, plane_state->base.visible);
+		assert_plane(plane, plane_state->slave ||
+			     plane_state->base.visible);
 }
 
 static void