[media] exynos4-is: Remove redundant MODULE_DEVICE_TABLE entries

Remove unneeded MODULE_DEVICE_TABLE(of,...) instances from files that
are linked into same module. This fixes following error when building
as a module:
LD [M]  drivers/media/platform/exynos4-is/s5p-fimc.o
drivers/media/platform/exynos4-is/fimc-is-sensor.o: In function `.LANCHOR1':
fimc-is-sensor.c:(.rodata+0x48): multiple definition of `__mod_of_device_table'
drivers/media/platform/exynos4-is/fimc-is.o:fimc-is.c:(.rodata+0x174): first defined here
drivers/media/platform/exynos4-is/fimc-is-i2c.o:(.rodata+0x5c): multiple definition of `__mod_of_device_table'
drivers/media/platform/exynos4-is/fimc-is.o:fimc-is.c:(.rodata+0x174): first defined here
make[4]: *** [drivers/media/platform/exynos4-is/exynos-fimc-is.o] Error 1
Also remove exporting fimc_is_(un)register_i2c_driver functions, it
is not needed since these functions should be called only from our
module.

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>