media: ivsc: csi: Make use of sub-device state

The MEI CSI driver was using sub-device state but still maintained its own
format information and did its own locking. Rely on sub-device state
instead. This also fixes a circular locking problem during link
validation.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>