drm/i915: Don't set plane visible during HW readout if CRTC is off

We already ensure that pstate->visible = false when crtc->active = false
during runtime programming; make sure we follow the same logic when
reading out initial hardware state.
Signed-off-by: NMatt Roper <matthew.d.roper@intel.com>
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Smoke-tested-by: NPaulo Zanoni <przanoni@gmail.com>
Link: http://patchwork.freedesktop.org/patch/59564/

drivers/gpu/drm/i915/intel_display.c

@@ -15175,7 +15175,7 @@ static void readout_plane_state(struct intel_crtc *crtc)
 	struct intel_plane_state *plane_state =
 		to_intel_plane_state(primary->state);
 
-	plane_state->visible =
+	plane_state->visible = crtc->active &&
 		primary_get_hw_state(to_intel_plane(primary));
 
 	if (plane_state->visible)