[media] adv7842: obtain free-run mode from the platform_data

The free-run mode can be board-specific.

Also updated the platform_data in ezkit to ensure that what was the old
default value is now explicitly specified, so the behavior for that board
is unchanged.

Signed-off-by: Martin Bugge <marbugge@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Scott Jiang <scott.jiang.linux@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>