staging/vc04_services/bcm2835-camera: distinct numeration and names for devices

staging/vc04_services/bcm2835-camera: distinct numeration and names for devices

Create a static atomic counter for numerating cameras.
Use the Media Subsystem Kernel Internal API to create distinct
device-names, so that the camera-number (given by the counter)
matches the camera-name.

Co-developed-by: Kay Friedrich <kay.friedrich@fau.de>
Signed-off-by: Kay Friedrich <kay.friedrich@fau.de>
Signed-off-by: Michael Kupfer <michael.kupfer@fau.de>
Link: https://lore.kernel.org/r/20191206085432.19962-1-michael.kupfer@fau.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>