RUI UART Uninitialize

RUI_RETURN_STATUS rui_uart_unint(RUI_UART_DEF uart_def);

@brief	This API is used to uninitialize UART.
@return	RUI_RETURN_STATUS
@param	RUI_UART_DEF uart_def: the instance of UART.
@module	RAK811, RAK4200, RAK4400, RAK4600, and RAK5010.