media: microchip-isc: Use accessors for pad config 'try_*' fields
The 'try_*' fields of the v4l2_subdev_pad_config structure are meant to
be accessed through helper functions. Replace direct access with usage
of the v4l2_subdev_get_pad_format(), v4l2_subdev_get_pad_crop() and
v4l2_subdev_get_pad_compose() helpers.