[media] ivtv: simplify how the decoder controls are set up

The code was unnecessarily complex, introducing a hdl_out handler that was
not needed. Instead just add the controls to the cxhdl.hdl handler directly.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>