[media] radio: wl128x: Update registration process with ST

As underlying ST driver registration API's have changed with
latest 2.6.38-rc8 kernel this patch will update the FM driver
accordingly.

Signed-off-by: Manjunatha Halli <manjunatha_halli@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>