V4L/DVB (6579): Fix bug #8824: Correct support for Diseqc on tda10086

This is a modified version of a patch previously posted by Thomas
Unverzagt.

Signed-off-by: Hartmut Hackmann <hartmut.hackmann@t-online.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>