V4L/DVB (12076): gspca_ov519: Fix led inversion with some cams

My ov519 cam has it led inverted, the same has been
reported on the ov51x-jpeg list for another
creative cam. This patch fixes this without changing
the behaviour for other cams.

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