[media] exynos4-is: use devm_of_platform_populate()

Usage of devm_of_platform_populate() simplify driver code
and save somes lines

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>