drivers: net: Register Micrel ksz884x network devices in PCI device tree.

This unifies the behaviour with other network device drivers and
allows for a matching of the PCI device path in UDEV rules.

Signed-off-by: Markus Lottmann <markus.lottmann1986@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>