ARM: dts: exynos: add 'chassis-type' property

A new 'chassis-type' root node property has recently been approved for
the device-tree specification.

Add this property for end-user devices (such as laptops,
smartphones and tablets) based on Samsung Exynos ARM SoCs.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20211017101228.19478-2-krzysztof.kozlowski@canonical.com