smsc95xx: add support for LAN9512 and LAN9514

LAN9512 and LAN9514 are USB hubs with an integrated 10/100 ethernet
controller.  Logically this looks like an ethernet controller (similar
to LAN9500) permanently attached to one of the hub's downstream ports.

This patch adds the usb device id of the new ethernet controller to the
smsc95xx driver.  This id is the same in both new devices.

Signed-off-by: Steve Glendinning <steve.glendinning@smsc.com>
Signed-off-by: David S. Miller <davem@davemloft.net>