[media] rtl2832.c: minor cleanup

The current formulation of the bw_params loop uses the counter j as an
index for the first dimension of the bw_params array which is later
incremented by the variable i. It is evaluated correctly only, because j
is initialized to 0 at the beginning of the loop. I think that
explicitly using the index 0 better reflects the intent of the
expression.

Signed-off-by: Hans-Frieder Vogt <hfvogt@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>