[media] rc-loopback: remove duplicate line

This patch just removes the second assignment "rc->priv = &loopdev;"
that happens a fews lines after the first one.

Signed-off-by: Michel Machado <michel@digirati.com.br>
CC: Mauro Carvalho Chehab <mchehab@infradead.org>
CC: "David Härdeman" <david@hardeman.nu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>