media: imx: imx7-media-csi: Fix mbus framefmt field init

'field' is zero-initialized to V4L2_FIELD_ANY, which is an invalid value
to return to userspace. Instead default to non-interleaving.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>