drm/tidss: crtc: Implement destroy_state

The tidss crtc driver implements its own state, with its own
implementation of reset and duplicate_state, but uses the default
destroy_state helper.

This somewhat works for now because the drm_crtc_state field in
tidss_crtc_state is the first field so the offset is 0, but it's pretty
fragile and it should really have its own destroy_state implementation.

Reviewed-by: Thomas Zimmermann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Maxime Ripard <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/tidss/tidss_crtc.c

···
 	tidss_runtime_put(tidss);
 }
 
+static void tidss_crtc_destroy_state(struct drm_crtc *crtc,
+				     struct drm_crtc_state *state)
+{
+	struct tidss_crtc_state *tstate = to_tidss_crtc_state(state);
+
+	__drm_atomic_helper_crtc_destroy_state(&tstate->base);
+	kfree(tstate);
+}
+
 static void tidss_crtc_reset(struct drm_crtc *crtc)
 {
 	struct tidss_crtc_state *tstate;
···
 	.set_config = drm_atomic_helper_set_config,
 	.page_flip = drm_atomic_helper_page_flip,
 	.atomic_duplicate_state = tidss_crtc_duplicate_state,
-	.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
+	.atomic_destroy_state = tidss_crtc_destroy_state,
 	.enable_vblank = tidss_crtc_enable_vblank,
 	.disable_vblank = tidss_crtc_disable_vblank,
 };