[media] exynos4-is: Preserve state of controls between /dev/video open/close

This patch moves the code for inheriting subdev v4l2 controls on the
FIMC video capture nodes from open()/close() fops to the link setup
notification callback. This allows for the state of the FIMC controls
to be always kept, in opposite to the current situation when it is
lost when last process closes video device.
There is no visible change for the original V4L2 compliant interface.
For the MC aware applications (user_subdev_api == true) inheriting
of the controls is dropped, since there can be same controls on the
subdevs withing single pipeline, now when the ISP (FIMC-IS) is also
used.
This patch is a prerequisite to allow /dev/video device to be opened
without errors even if there is no media links connecting it to an
image source (sensor) subdev. This is required for a libv4l2 plugin
to be initialized while a video node is opened and it also should be
possible to always open the device to query the capabilities.

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>