ARM: dts: exynos: Fix DTC unit name warnings in Exynos4x12

Fix following DTC warnings in Exynos4x12 boards:

Warning (unit_address_vs_reg): Node /camera/fimc-is@12000000/pmu has a reg or ranges property, but no unit name

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>