ARM: dts: exynos: Add Ethernet interface description for Odroid U3

Add Ethernet interface description for Odroid U3.

Add an alias to enable bootloaders to find the Ethernet interface
and assign a MAC address.

Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
Link: https://lore.kernel.org/r/20201103184412.18874-6-l.stelmach@samsung.com


Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>