The flag PDN_INV indicates that the sensor pin S_PWR_DN has not the same
value as other webcams with the same sensor. For now, only two webcams have
been so detected: the Microsoft's VX1000 and VX3000.

Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>