V4L/DVB (7641): V4L: ov511 - use usb_interface as parent, not usb_device

The current code creates a bogus DEVPATH:
  /devices/pci0000:00/0000:00:1d.0/usb1/1-2/video4linux/video0
while it should be:
  /devices/pci0000:00/0000:00:1d.0/usb1/1-2/1-2:1.0/video4linux/video0

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>