V4L/DVB (13194): gspca - gl860: improvement of the main driver part

- fix for warning compilation about sd_ctrls
- trace improvement while probing the sensor

Signed-off-by: Olivier Lorin <o.lorin@laposte.net>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>