Add KSZ8851SNL Ethernet driver (IDFGH-4736)

[b1ackviking]

Is your feature request related to a problem? Please describe.

I'm adding support for KSZ8851SNL, a single-port Ethernet controller with SPI, in one of our company's projects. ESP-IDF does not support it at the moment, but fortunately, I'm allowed to share the code under an open-source license.

Describe the solution you'd like

I'm going to develop and contribute the driver for KSZ8851SNL to the ESP-IDF project.

Describe alternatives you've considered

We have discussed with our project manager the pros and cons of open-sourcing the driver versus keeping it in-house and came up with the decision to make it public.

Additional context

I'm planning to add the driver into the esp_eth component, similar to the other Ethernet controller drivers.

[suda-morris]

Cool, nice to have more Ethernet module support.