[media] dvb-frontends/cxd2841er: more configurable TSBITS

Bits 3 and 4 of the TSCONFIG register are important for certain hardware
constellations, in that they need to be zeroed. Add a configuration flag
to toggle this.

Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Acked-by: Abylay Ospan <aospan@netup.ru>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>