BCM63168 has 6 ports (3 FE PHY, 1 GE PHY, two RGMII) and BCM63268
has two additional RGMII ports, making it 8.
Fix this by checking the chip variant and applying an appropriate
limit.
Signed-off-by: Jonas Gorski <jogo@openwrt.org>
SVN-Revision: 39677