brcm47xx: use lib phy when tg3 is in use

This is untested, but probably needed to make it work with the phy lib switch driver.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37649 3c298f89-4303-0410-b956-a3cf2f4a3e73