Save some flash on radios w/o software controllable serial port power supply pins.

radio/src/serial.cpp

@@ -331,9 +331,11 @@ void serialInit(uint8_t port_nr, int mode)
       if (port->uart && port->uart->init)
         state->usart_ctx = port->uart->init(&params);
 
+#if defined(SWSERIALPOWER)
       // Set power on/off
       if (port_nr < SP_VCP)
         serialSetPowerState(port_nr);
+#endif
     }
 
     // Update callbacks once the port is setup