[media] exynos4-is: Add clock provider for the SCLK_CAM clock outputs

This patch adds clock provider so the the SCLK_CAM0/1 output clocks
can be accessed by image sensor devices through the clk API.

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