[media] drxk: Add pre/post BER and PER/UCB stats

The original az6007 driver has the code to calculate such
stats. Add it to the driver, reporting them via DVBv5
stats API.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --cc drivers/media/dvb-frontends/drxk_hard.c
Simple merge

diff --cc drivers/media/dvb-frontends/drxk_hard.h
Simple merge

diff --cc drivers/media/dvb-frontends/drxk_map.h
Simple merge