media: imx: imx7-mipi-csis: Remove link setup on source pad

The driver rejects enablement of multiple links on its source pad. This
isn't needed, as the CSIS doesn't care. Drop it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>