v4l/dvb: Fix budget-av frontend detection

The budget-av needs this GPIO set low for most cards to work.

Signed-off-by: Andrew de Quincey <adq_dvb@lidskialf.net>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>