V4L/DVB (11488): get_dvb_firmware: trivial url change

Trivial url changes in script

Signed-off-by: Joseba Goitia Gandiaga <josebagg@gmail.com>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>