tg3: make it possible to provide phy_id in ioctl

In OpenWrt we currently use a switch driver which uses the ioctls to
configure the switch in the phy. We have to provide the phy_id to do
so, but without this patch this is not possible.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>