disp: msm: sde: destroy framebuffers after plane cleanup

Add framebuffer destroy immediately following plane cleanup
during secure display transition. Set state's fb to NULL
after destroying to avoid attempting to destroy fb again
during plane state destroy. Previously, framebuffer destroy
is happening after the context is detached while plane states
are being destroyed.

Change-Id: I273ce5b85c30962ea7e0a738a366487c9c85d4df
Signed-off-by: Samantha Tran <samtran@codeaurora.org>

msm/sde/sde_plane.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2019, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2015-2020, The Linux Foundation. All rights reserved.
  * Copyright (C) 2013 Red Hat
  * Author: Rob Clark <robdclark@gmail.com>
  *
@@ -133,6 +133,12 @@ struct sde_multirect_plane_states {
 #define sde_plane_get_property(S, X) ((S) && ((X) < PLANE_PROP_COUNT) ? \
 	((S)->property_values[(X)].value) : 0)
 
+/**
+ * sde_plane_destroy_fb - destroy fb object and clear fb
+ * @state: old plane state
+ */
+void sde_plane_destroy_fb(struct drm_plane_state *state);
+
 /**
  * sde_plane_pipe - return sspp identifier for the given plane
  * @plane:   Pointer to DRM plane object