V4L/DVB (6015): DVB: convert struct class_device to struct device

The currently used "struct class_device" will be removed from the
kernel. Here is a trivial patch that converts DVB to use struct device.

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