drm/amd/display: implement dc_init_callbacks to assign callback pointers after dc_create

[why]
Some components depend on dc to constuct
but need to assign callback functions to dc.

[how]
Instead of assigning dc callback functions in dc_create,
decouple the callback init to a standlone function after dc_create. This
is currently a no-op.
Signed-off-by: Wenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc.c

@@ -840,6 +840,11 @@ struct dc *dc_create(const struct dc_init_data *init_params)
 	return NULL;
 }
 
+void dc_init_callbacks(struct dc *dc,
+		const struct dc_callback_init *init_params)
+{
+}
+
 void dc_destroy(struct dc **dc)
 {
 	destruct(*dc);

drivers/gpu/drm/amd/display/dc/dc.h

@@ -339,8 +339,13 @@ struct dc_init_data {
 	uint32_t log_mask;
 };
 
-struct dc *dc_create(const struct dc_init_data *init_params);
+struct dc_callback_init {
+	uint8_t reserved;
+};
 
+struct dc *dc_create(const struct dc_init_data *init_params);
+void dc_init_callbacks(struct dc *dc,
+		const struct dc_callback_init *init_params);
 void dc_destroy(struct dc **dc);
 
 /*******************************************************************************