Silicon Labs 210x USB to UART Bridge refers to the USB to UART device and driver your programmer is using, it does not explain anything about the programmer or circuit you are using. To program 89C2051 you need a 12V circuit for the reset pin. This mcu only can be programmed in parallel mode.
Why not use another mcu that can be programmed with ISP? (89S2051, 89S51)
Do some research and you will learn. There are many websites with information on building one of these programmers.