arm64: dts: renesas: draak: Remove unnecessary index from vin4 port

The ports node of vin4 only has one sub-node and thus does
not need #address-cells/#size-cells and the sub-node does
not need an exit.

This addresses the following warning:

 # make dtbs W=1
 ...
 arch/arm64/boot/dts/renesas/r8a77995-draak.dts:492.8-503.4: Warning (graph_child_address): /soc/video@e6ef4000/ports: graph node has single child node 'port@0', #address-cells/#size-cells are not necessary

Fixes: 6a0942c2 ("arm64: dts: renesas: draak: Describe CVBS input")
Cc: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>