media: exynos4-is: Correct missing entity function initialization

Commit bae45003 ("[media] exynos4-is: Add missing entity function
initialization") tried to suppress the warnings such as

s5p-fimc-md camera: Entity type for entity FIMC.0 was not initialized!

However, this missed setting for the subdev.  Set it now to avoid the
ugly warnings on boot.

Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>