arm64: dts: renesas: rcar-gen3: Replace "vsps" by "renesas,vsps"

The Renesas-specific "vsps" property lacks a vendor prefix.
Add a "renesas," prefix to comply with DT best practises.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20191105183504.21447-4-geert+renesas@glider.be