media: v4l2-subdev: Fix stream handling for crop API

When support for streams was added to the V4L2 subdev API, the
v4l2_subdev_crop structure was extended with a stream field, but the
field was not handled in the core code that translates the
VIDIOC_SUBDEV_[GS]_CROP ioctls to the selection API. Fix it.

Fixes: 2f91e10e ("media: subdev: add stream based configuration")
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>