V4L/DVB: tda10048: fix bitmask for the transmission mode

Add a missing bit for reading the transmission mode (2K/8K) in
tda10048_get_tps

Signed-off-by: Guillaume Audirac <guillaume.audirac@webag.fr>
Signed-off-by: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>