[media] dib8000: Fix UCB measure with DVBv5 stats

On dib8000, the block error count is a monotonic 32 bits register.
With DVBv5 stats, we use a 64 bits counter, that it is reset
when a new channel is tuned.

Change the UCB counting start from 0 and to be returned with
64 bits, just like the API requests.

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