arm64: dts: renesas: r8a7799[05]: Point LVDS0 to its companion LVDS1

Add the new renesas,companion property to the LVDS0 node to point to the
companion LVDS encoder LVDS1.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Tested-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>