[media] exynos4-is: Remove dependency on PM_RUNTIME from Kconfig

Now when the sub-drivers are fixed to work with runtime PM disabled
this erroneous dependency can be removed.
The CAM and ISP power domains should be left in active state by the
platform if runtime PM is not used.

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