dp: application: log when starting the thread

Add a single information level log entry when the userspace DP thread
starts.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>

Author: lyakh

src/schedule/zephyr_dp_schedule_application.c

@@ -283,6 +283,7 @@ void dp_thread_fn(void *p1, void *p2, void *p3)
 
 	/* The IPC thread is waiting for the thread to be started, it can proceed now. */
 	k_sem_give(&dp_sync[task->core]);
+	comp_info(pmod->dev, "userspace thread started");
 
 	do {
 		/*