[media] cx23885: Declare MODULE_FIRMWARE usage

Cc: Steven Toth <stoth@kernellabs.com>
Cc: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>