Sample pinmux file for AM5718 IDK EVM rev 1.3A and 1.3B
4-port: provides two 10/100/1000 (RGMII) + two 10/100 (PRU ICSS MII) + LCD panel
6-port: provides two 10/100/1000 (RGMII) + four 10/100 (PRU ICSS MII) without LCD panel

Use jumper J51 on the EVM board to select the multiplexing option.
Older boards require moving zero-ohm resistors. Find support on E2E or through your TI representative. 

6-port config is only possible with AM571x and AM574x families.