[media] exynos4-is: Use common exynos_media_pipeline data structure

This enumeration is now private to exynos4-is and the exynos5 camera
subsystem driver may have the subdevs handling designed differently.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>