V4L/DVB (10497): saa7146: i2c adapdata now points to v4l2_device.

Prepare for converting to v4l2_subdev.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>