[media] dvb: get rid of fepriv->parameters_in

This var were used during DVBv3 times, in order to keep a copy
of the parameters used by the events. This is not needed anymore,
as the parameters are now dynamically generated from the DVBv5
structure.

So, just get rid of it. That means that a DVBv5 pure call won't
use anymore any DVBv3 parameters.

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