[media] media: mx1_camera: use the default .set_crop() implementation

.set_crop() implementation in mx1_camera is identical with the default.
Remove the copy to switch to using the default stab.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>