Port CRSF RC driver to new Serial UART API (#22917)

* Added implementations of Rx Tx swap and single wire for new UART API needed by CRSF driver
* Added inverted mode to Serial interface API

platforms/posix/include/SerialImpl.hpp

@@ -64,6 +64,8 @@ public:
 
 	ssize_t write(const void *buffer, size_t buffer_size);
 
+	void flush();
+
 	const char *getPort() const;
 	static bool validatePort(const char *port);
 	bool setPort(const char *port);
@@ -83,6 +85,15 @@ public:
 	FlowControl getFlowcontrol() const;
 	bool setFlowcontrol(FlowControl flowcontrol);
 
+	bool getSingleWireMode() const;
+	bool setSingleWireMode();
+
+	bool getSwapRxTxMode() const;
+	bool setSwapRxTxMode();
+
+	bool getInvertedMode() const;
+	bool setInvertedMode(bool enable);
+
 private:
 
 	int _serial_fd{-1};
@@ -100,6 +111,10 @@ private:
 
 	bool validateBaudrate(uint32_t baudrate);
 	bool configure();
+
+	bool _single_wire_mode{false};
+	bool _swap_rx_tx_mode{false};
+	bool _inverted_mode{false};
 };
 
 } // namespace device