[media] s5p-fimc: Add runtime PM support in the mem-to-mem driver

Add runtime PM and system sleep support in the memory-to-memory
driver. It's required to enable the FIMC operation on Exynos4
SoCs. This patch prevents system boot failure when the driver
is compiled in, as it now tries to access its I/O memory without
first enabling the corresponding power domain.

The camera capture device suspend/resume is not fully covered,
the capture device is just powered on/off during the video
node open/close. However this enables it's normal operation
on Exynos4 SoCs.

[mchehab@redhat.com: fix a small checkpatch error]
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>