media: ti: cal: Use subdev state

Change TI CAL driver to use subdev state. No functional changes
(intended).

This allows us to get rid of the 'formats' field, as the formats are
kept in the state, and also the 'mutex' as we already have state locking.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>