ARM: dts: exynos: Remove "simple-bus" compatible from fimc-is node

The "simple-bus" compatible was originally added for fimc-is only
to ensure the child devices instantiation.  The child devices are
now being created by the parent device driver so remove the
"simple-bus" compatible.

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