V4L/DVB: IR/imon: remove incorrect calls to input_free_device

Per Dmitry Torokhov, following input_unregister_device with an
input_free_device is forbidden, the former is sufficient alone.

Acked-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>