[media] exynos4-is: Fix FIMC-IS clocks initialization

The ISP clock register content is not preserved over the ISP power domain
off/on cycle. Instead of setting the clock frequencies once at probe time
the clock rates set up is moved to the runtime_resume handler, which is
invoked after the related power domain is already enabled, ensuring the
clocks are properly configured when the device is actively used.
This fixes the FIMC-IS malfunctions and STREAM ON timeout errors accuring
on some boards:
[ 59.860000] fimc_is_general_irq_handler:583 ISR_NDONE: 5: 0x800003e8, IS_ERROR_UNKNOWN
[ 59.860000] fimc_is_general_irq_handler:586 IS_ERROR_TIME_OUT

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>