V4L/DVB (11325): soc-camera: fix breakage caused by 1fa5ae85

soc-camera re-uses struct devices multiple times in calls to device_register(),
therefore it has to reset the embedded struct kobject to avoid the "tried to
init an initialized object" error, which then also erases its name. Now with
the transition to kobject's name for device names, we have to re-initialise the
name before each call to device_register().

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>