[media] DVB: dib0700, move Nova-TD Stick to a separate set

To properly support the three LEDs which are on the stick, we need
a special handling in the ->frontend_attach function. Thus let's have
a separate ->frontend_attach instead of ifs in the common one.

The hadnling itself will be added in further patches.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Patrick Boettcher <pboettcher@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>