[media] s5p-fimc: Add the media device driver

Add a top level media device driver aggregating FIMC video devnodes,
MIPI-CSIS and sensor subdevs. This driver gathers all media entities
and creates the possible links between them during initialization. By
default some links will be activated to enable access to all available
sensors in the system. For example if there are sensors S0, S1 listed
in the media device platform data definition they will be by default
assigned to FIMC0, FIMC1 respectively, which in turn will corresponds
to separate /dev/video?.
There is enough FIMC H/W entities to cover all available physical camera
interfaces in the system.

The fimc media device driver is bound to the "s5p-fimc-md" platform device.
Such platform device should be created by board initialization code
and camera sensors description array need to be specified as its
platform data.

The media device driver also implements various video pipeline operations,
for enabling subdevs power, streaming, etc., which will be used by the
capture video node driver.

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>