ARM: at91/net: add macb ethernet controller in 9g45/9g20 DT

Add the Cadence macb ethernet controller in at91sam9g45 and at91sam9g20
.dtsi and enable it in at91sam9m10g45ek and usb_a9g20 board device tree file.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>