media: imx: Clear fwnode link struct for each endpoint iteration

In imx_media_create_csi_of_links(), the 'struct v4l2_fwnode_link' must
be cleared for each endpoint iteration, otherwise if the remote port
has no "reg" property, link.remote_port will not be reset to zero.
This was discovered on the i.MX53 SMD board, since the OV5642 connects
directly to ipu1_csi0 and has a single source port with no "reg"
property.

Fixes: 621b08ea

 ("media: staging/imx: remove static media link arrays")

Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>