V4L/DVB (4464): FIX_ AverTV A800 trouble

A new revision of the Avermedia A800 does not reenumerate after download the firmware.

Signed-off-by: Klaus Frahm <frahm@irsamc.ups-tlse.fr>
Signed-off-by: Martin Habbecke <M.Habbecke@gmx.de>
Signed-off-by: Patrick Boettcher <pb@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>