fixed error with removing module when there is no network registred, cleaned up code and updated readme

changed loop for finding pci devices to a while loop, pci_get_device returns NULL when all devices are found (works, tested with 2 cards)

Removed vmk180_serial_demo ip core, and use versal_network_device ip insted, which can be connected to Wupper. Changed the PCIe driver to use the Wupper device Bar 3 and corresponding registers