[media] v4l: Fix typo in v4l2_subdev_get_try_crop()

The helper function is defined by a macro that is erroneously called
with the compose rectangle instead of the crop rectangle. Fix it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>