Thank you for adding Nucleo-F439ZI support in v2.8.0

We make use of the STM32Ethernet library for our networked application on both the Nucleo-F429ZI and Nucleo-F439ZI, and have discovered an issue that suggests a custom PeripheralPins.c would be the appropriate answer.

The current code in STM32Ethernet's HAL_ETH_MspInit() routine in ethernetif.cpp blasts its way over every pin associated with Ethernet in the PeripheralPins.c, leaving pins not used on the Nucleo-F4[23]9ZI boards also configured with AF attributes.

We propose that a custom PeripheralPins_NUCLEO_F4x9ZI.c file be used, which limits this initialisation to just the pins actually used on both Nucleos.

Please find attached a proposed form of the file which we've tested. Or I can inssue a suitable PR if you'd prefer.
PeripheralPins_NUCLEO_F4x9ZI.c.zip