V4L/DVB (4955): Fix autosearch index

After rewriting the driver the wrong autosearch index was used when
COFDM-parameter needed to be detected.
Thanks to Mario Rossi who found it.

Signed-off-by: Mario Rossi <mariofutire@googlemail.com>
Signed-off-by: Patrick Boettcher <pb@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>