[media] exynos4-is: Add missing entity function initialization

Suppresses following warnings:

s5p-fimc-md camera: Entity type for entity FIMC.0 was not initialized!
s5p-fimc-md camera: Entity type for entity FIMC.1 was not initialized!
s5p-fimc-md camera: Entity type for entity s5p-mipi-csis.0 was not initialized!
s5p-fimc-md camera: Entity type for entity s5p-mipi-csis.1 was not initialized!
s5p-fimc-md camera: Entity type for entity FIMC-LITE.0 was not initialized!
s5p-fimc-md camera: Entity type for entity FIMC-LITE.1 was not initialized!
s5p-fimc-md camera: Entity type for entity FIMC-IS-ISP was not initialized!

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>