ARM: dts: Add FIMD node to exynos4

This patch adds a common FIMD device node for all Exynos4 SoCs.

Signed-off-by: Vikas Sajjan <vikas.sajjan@linaro.org>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>