[media] exynos4-is: Make fimc-lite independent of struct fimc_sensor_info

Make the sensor subdevs host_data hold a pointer to struct fimc_source_info,
which is defined in the driver's public header, rather than a pointer to
struct fimc_sensor_info which is specific to exynos4-is media device driver.
The purpose of this change is to allow easier reuse of the fimc-lite module
in the exynos5-is driver, which should similarly store a pointer to struct
fimc_source_info instance in the sensor's subdev host_data.

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>