net/ethernet/dec/tulip/xircom_cb: Use module_pci_driver to register driver

Removing some boilerplate by using module_pci_driver instead of calling
register and unregister in the otherwise empty init/exit functions.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Reviewed-by: Grant Grundler <grundler@parisc-linux.org>
Signed-off-by: David S. Miller <davem@davemloft.net>