net/fddi: Replace local macro with PCI standard macro

Replace local macro DFX_BUS_PCI() with PCI standard macro
dev_is_pci().

Acked-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>