mavlink: use send() instead of using reset flag

I think we can just directly use send() and don't need to use the
workaround of resetting the send flag to trigger one send.

Also, we don't need to override it if we don't need to check any params.

src/modules/mavlink/mavlink_stream.h

@@ -99,8 +99,7 @@ public:
 	virtual bool request_message(float param2 = 0.0, float param3 = 0.0, float param4 = 0.0,
 				     float param5 = 0.0, float param6 = 0.0, float param7 = 0.0)
 	{
-		reset_last_sent();
-		return true;
+		return send(hrt_absolute_time());
 	}
 
 	/**