V4L/DVB (10665): soc-camera: add data signal polarity flags to drivers

All soc-camera camera and host drivers must specify supported data signal
polarity, after all drivers are fixed, we'll add a suitable test to
soc_camera_bus_param_compatible().

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>