[media] s5p-fimc: Use v4l2_subdev internal ops to register video nodes

In order to be able to select only FIMC-LITE support, which is added
with subsequent patches, the regular FIMC support is now contained
only in fimc-core.c, fimc-m2m.c and fimc-capture.c files. The graph
and pipeline management is now solely handled in fimc-mdevice.[ch].
This means the FIMC driver can now be excluded with Kconfig option,
leaving only FIMC-LITE and allowing this driver to be reused in SoCs
that have only FIMC-LITE and no regular FIMC IP.

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>