[media] s5p-fimc: Conversion to use struct v4l2_fh

This is a prerequisite for the patch converting the driver to use
the control framework. As the capture driver does not use per file
handle contexts, two separate ioctl handlers are created for it
(vidioc_try_fmt_mplane, and vidioc_g_fmt_mplane) so there is no
handlers shared between the memory-to-memory and capture video node.

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>