qcacmn: Add provision for flush callback in scheduler message

Add provision for flush callback in scheduler message such that
during driver unload scheduler can invoke the flush callback and
components can release the common object ref count which is taken
before posting the message.

Change-Id: I28490e18247239af27feef3a4b53e5080ab012fc
CRs-Fixed: 2034772

scheduler/inc/scheduler_api.h

@@ -73,6 +73,11 @@ typedef enum {
  * @bodyval: message body val
  * @callback: callback to be called by scheduler thread once message is posted
  *   and scheduler thread has started processing the message.
+ * @flush_callback: flush callback which will be invoked during driver unload
+ *   such that component can release the ref count of common global objects
+ *   like PSOC, PDEV, VDEV and PEER. A component needs to populate flush
+ *   callback in message body pointer for those messages which have taken ref
+ *   count for above mentioned common objects.
  */
 struct scheduler_msg {
 	uint16_t type;
@@ -80,6 +85,7 @@ struct scheduler_msg {
 	void *bodyptr;
 	uint32_t bodyval;
 	void *callback;
+	void *flush_callback;
 };
 
 typedef QDF_STATUS (*scheduler_msg_process_fn_t) (struct scheduler_msg  *msg);