The readme file from the prism2.device archive says:
prism2.device is a SANA-II network driver for 11Mbps wireless Ethernet cards
based on the Prism II chipset and variants. It supports PCMCIA cards in the
A1200/A600 and PCI cards in AmigaOnes, Prometheus-equipped Amigas and PCs
running Amithlon.
So, I cannot use it on my Mediator-equipped Amiga?