dt-bindings: iommu: ipmmu-vmsa: Use generic node name

Use the preferred generic node name in the example.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: NSimon Horman <horms+renesas@verge.net.au>
Signed-off-by: NRob Herring <robh@kernel.org>

Documentation/devicetree/bindings/iommu/renesas,ipmmu-vmsa.txt

@@ -53,7 +53,7 @@ Example: R8A7791 IPMMU-MX and VSP1-D0 bus master
 		#iommu-cells = <1>;
 	};
 
-	vsp1@fe928000 {
+	vsp@fe928000 {
 		...
 		iommus = <&ipmmu_mx 13>;
 		...