V4L/DVB (11079): au0828: fix panic on disconnect if analog initialization failed

If the analog initialization failed to create the video device, we never
actually add the entry to the au0828_devlist.  Therefore a panic occurs when
unregistering the analog subsystem.

Make it so we only remove the entry from the list if we added it to the list
in the first place.

Signed-off-by: Devin Heitmueller <dheitmueller@linuxtv.org>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>