V4L/DVB (4122): Lgdt330x: fix missing line in VSB snr decoding logic

- fix missing line in VSB snr decoding logic for lgdt3303

Signed-off-by: Mac Michaels <wmichaels@earthlink.net>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>