[media] exynos4-is: Compile in fimc-lite runtime PM callbacks conditionally

Enclose the runtime PM helpers in #ifdef CONFIG_PM_RUNTIME/#endif
to avoid following compile warning when CONFIG_PM_RUNTIME is disabled:

CC      drivers/media/platform/exynos4-is/fimc-lite.o
drivers/media/platform/exynos4-is/fimc-lite.c:1591:12: warning: ‘fimc_lite_runtime_resume’ defined but not used [-Wunused-function]
drivers/media/platform/exynos4-is/fimc-lite.c:1599:12: warning: ‘fimc_lite_runtime_suspend’ defined but not used [-Wunused-function]

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