drm/i915: Clear old hw.fb & co. from slave plane's state

Let's do the intel_plane_copy_uapi_to_hw_state() before we bail out
due to both old and new uapi.crtc being NULL. This will drop the
reference to the old hw.fb for planes that are transitioning from
being a slave plane to simply being disabled.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200110183228.8199-2-ville.syrjala@linux.intel.comReviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/display/intel_atomic_plane.c

@@ -225,12 +225,9 @@ int intel_plane_atomic_check_with_state(const struct intel_crtc_state *old_crtc_
 					struct intel_plane_state *new_plane_state)
 {
 	struct intel_plane *plane = to_intel_plane(new_plane_state->uapi.plane);
-	const struct drm_framebuffer *fb;
+	const struct drm_framebuffer *fb = new_plane_state->hw.fb;
 	int ret;
 
-	intel_plane_copy_uapi_to_hw_state(new_plane_state, new_plane_state);
-	fb = new_plane_state->hw.fb;
-
 	new_crtc_state->active_planes &= ~BIT(plane->id);
 	new_crtc_state->nv12_planes &= ~BIT(plane->id);
 	new_crtc_state->c8_planes &= ~BIT(plane->id);
@@ -292,6 +289,7 @@ int intel_plane_atomic_check(struct intel_atomic_state *state,
 	const struct intel_crtc_state *old_crtc_state;
 	struct intel_crtc_state *new_crtc_state;
 
+	intel_plane_copy_uapi_to_hw_state(new_plane_state, new_plane_state);
 	new_plane_state->uapi.visible = false;
 	if (!crtc)
 		return 0;

drivers/gpu/drm/i915/display/intel_display.c

@@ -16018,6 +16018,8 @@ intel_legacy_cursor_update(struct drm_plane *_plane,
 	new_plane_state->uapi.crtc_w = crtc_w;
 	new_plane_state->uapi.crtc_h = crtc_h;
 
+	intel_plane_copy_uapi_to_hw_state(new_plane_state, new_plane_state);
+
 	ret = intel_plane_atomic_check_with_state(crtc_state, new_crtc_state,
 						  old_plane_state, new_plane_state);
 	if (ret)