arm64: dts: renesas: r8a77965: Add VSP instances

The r8a77965 has 4 VSP instances.

Based on a similar patch of the R8A7796 device tree
by Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>.

Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
[Kieran: Rebased to top of tree, fixed sort orders]
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>