[media] cx23885: Fix tuning regression for TeVii S471

When tuning to 10818V on Astra 28E2, the system tunes to 11343V
instead. This is a regression in the S471 driver introduced with the
changeset: b43ea806 [media] cx23885:
Fix TeVii S471 regression since introduction of ts2020.

Suggested-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

Signed-off-by: Joakim Hernberg <jhernberg@alchemy.lu>
Tested-by: Mark Clarkstone <hello@markclarkstone.co.uk>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>