The exynos5440 device tree is the only one left, which does not use
"soc" node. Add a "soc" node to exynos5440.dtsi in order to make it
consistent with other exynos DTS.
Signed-off-by: NMaciej Purski <m.purski@samsung.com>
Signed-off-by: NKrzysztof Kozlowski <krzk@kernel.org>