[media] s5p-fimc: Limit number of available inputs to one

[media] s5p-fimc: Limit number of available inputs to one

The current driver allowed camera sensors to be used only with single
FIMC H/W instance, FIMC0..FIMC2/3, designated at compile time. Remaining FIMC
entities could be used for video processing only, as mem-to-mem devices.
Required camera could be selected with S_INPUT ioctl at one devnode only.

However in that case it was not possible to use both cameras independently
at the same time, as all sensors were registered to single FIMC capture
driver. In most recent S5P SoC version there is enough FIMC H/W instances
to cover all physical camera interfaces.
Each FIMC instance exports its own video devnode. Thus we distribute
the camera sensors one per each /dev/video? by default. It will allow to
use both camera simultaneously by opening different video node.

The camera sensors at FIMC are now not selected with S_INPUT ioctl, there
is one input only available per /dev/video?.

By default a single sensor is connected at FIMC input as specified by the
media device platform data subdev description table. This assignment
can be changed at runtime through the pipeline reconfiguration at the media
device level.

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>