[Future] Also log 'res' in LOGD of setCompletion(int32_t res)

It can't hurt to provide more information in log messages, especially 'res' is a good candidate in this case.

emper/io/Future.hpp

@@ -140,7 +140,7 @@ class Future : public Logger<LogSubsystem::IO> {
 
 	void setCompletion(int32_t res) {
 		assert(!state.completed);
-		LOGD("Complete " << this);
+		LOGD("Complete " << this << " with result " << res);
 		returnValue = res;
 		state.completed = true;
 	}