media: v4l2-subdev: Rename pad config 'try_*' fields

The try_fmt, try_crop and try_compose fields of the
v4l2_subdev_pad_config structure are misnamed (for historical reason) as
they also store data for the subdev active configuration. Rename them to
format, crop and compose respectively and update the accessor helpers.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>