V4L/DVB (5701): Documentation/dvb/bt8xx.txt update

This patch synchronizes the Documentation for bt8xx-based cards to the
actual state of kernel 2.6.22-rc1.

Signed-off-by: Uwe Bugla <uwe.bugla@gmx.de>
Signed-off-by: Manu Abraham <manu@linuxtv.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>