[media] cx231xx: Improve the log message

[media] cx231xx: Improve the log message

Unfortunately, on devices that have multiple interfaces, udev->dev
points to the parent device (usb) instead of the cx231xx specific one.

Due to that the logs don't look too nice, as they'll print messages
as if they were produced by USB core:
  usb-1-2: New device Conexant Corporation Polaris AV Capturb @ 480 Mbps (1554:5010) with 7 interfaces

Instead of using the name of the parent device, let's use the name
of the first cx231xx interface for all cx231xx sub-modules.

With this path, the logs will be nicer:

  cx231xx 1-2:1.1: New device Conexant Corporation Polaris AV Capturb @ 480 Mbps (1554:5010) with 7 interfaces

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>