PCI Core does not support multi-function function.

With Header Type of Configuration Register, bit 7 can be used to determine whether the multi-function function is supported or not.
The user guide states "0", so it is unsupported.

This can be confirmed from the Header Type in the User Guide at the URL link below.
Please refer to it by searching with the keyword "Header Type Register".
https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/ug/ug_pci.pdf

For multi-function, please use other company's PCI Core.