ARM: dts: exynos: Add "syscon" compatible string to chipid node on Exynos5

The Chip ID block in addition to exact chip revision information
contains data and control registers for ASV (Adaptive Supply Voltage)
and ABB (Adaptive Body Bias). Add "syscon" compatible so the Chip ID
block can be shared by respective drivers.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>