ARM: dts: exynos: Add initial support for Odroid XU board

The Hardkernel's Odroid XU board was first design with big.LITTLE SoC
from Samsung: the Exynos5410. Details:
1. Exynos5410 octa-core (A15+A7, however as of now only one cluster is
   enabled),
2. 2 GB DDR3 RAM,
3. PowerVR SGX544MP3 GPU (not enabled in DTS),
4. USB 3.0 Host x 1, USB 3.0 OTG x 1, USB 2.0 Host x 4,
5. HDMI 1.4a, MIPI DSI and Display Port (Display Port not on all of
   revisions though),
6. eMMC 4.5 and microSD slots.

Comparing this board to Odroid XU3 (more popular), the differences are:
1. Exynos5410 instead of 5422,
2. MIPI DSI LCD connector,
3. Main PMIC: Maxim 77802 instead of S2MPS11,
4. USB3503+LAN9730 instead of integrated LAN9514,
5. eMMC 4.5 instead of eMMC 5.0,

This patch adds initial support for the XU board with working basic
functions, eMMC/SD and USB (including attached ethernet adapter).

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Link: http://www.hardkernel.com/main/products/prdt_info.php?g_code=G137510300620