[media] s5p-csis: Rework the system suspend/resume helpers

Do not resume the device during system resume if it was idle
before system suspend, as this causes resume from suspend
to RAM failures on Exynos4. For this purpose runtime PM and
system sleep helpers are separated.

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>