[media] gspca: s/strncpy/strlcpy/

Just like in userspace strncpy does not guarantee 0 termination. Use strlcpy
instead which does guarantee 0 termination.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>