ARM: dts: berlin: Add BG2CD ethernet DT nodes

Marvell BG2CD has two fast ethernet controllers with internal PHY,
add the corresponding nodes to SoC dtsi.

Tested-by: Antoine Ténart <antoine.tenart@free-electrons.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>