[media] cxd2820r: remove unused parameter from cxd2820r_attach

Fix bug introduced by multi-frontend to single-frontend change.
This parameter is no longer used after multi-frontend to single-frontend change.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>