modbus-rtu: esp-idf port, make sure line endings are ignored on UART

By default some line ending conversion may be done, so make sure to
disable this on the UART used with libmodbus.

src/modbus-rtu.c

@@ -588,6 +588,8 @@ static int _modbus_rtu_connect(modbus_t *ctx)
     }
 
     uart_vfs_dev_use_driver(uart_num);
+    uart_vfs_dev_port_set_rx_line_endings(uart_num, ESP_LINE_ENDINGS_LF);
+    uart_vfs_dev_port_set_tx_line_endings(uart_num, ESP_LINE_ENDINGS_LF);
 
     return 0;
 }