[media] tw9910: init priv->scale and update standard

When the standard changes the VACTIVE and VDELAY values need to be updated.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>