V4L/DVB (10464): radio-si470x: use usb_make_path in usb-radio drivers

Place usb_make_path in radio-si470x.c that used when reporting bus_info
information in vidioc_querycap.

Acked-by: Tobias Lorenz <tobias.lorenz@gmx.net>
Signed-off-by: Alexey Klimov <klimov.linux@gmail.com>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>