[media] tda18271: fix calculation bug in tda18271_rf_tracking_filters_init

Misplaced parenthesis cause a calculation bug in
tda18271_rf_tracking_filters_init

Thanks to Stefan Sibiga for pointing this out.

Cc: Stefan Sibiga <stefansibiga@yahoo.ca>
Signed-off-by: Michael Krufky <mkrufky@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>