[media] exynos4-is: Handle suspend/resume of fimc-is-i2c correctly

If the same callbacks are used for runtime and system suspend/resume,
clocks can get disabled twice, which can lead to negative reference
counts and kernel warnings.
This patch splits suspend/resume callbacks into separate runtime and
system-wide functions, so clock gating is done correctly.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>