[media] dib8000: Fix: add missing 4K FFT mode

Without that, tuning may fail on 4K FFT mode, as the transmission
parameter cache will be initialized with a wrong value.

Acked-By: Patrick Boettcher <pboettcher@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>