ARM: dts: imx1: Use 'bus' for AIPI bus

Per simple-bus.yaml, 'aipi' is not a valid node name.

Change it to 'bus' to fix the following dt-schema warning:

imx1-apf9328.dtb: aipi@200000: $nodename:0: 'aipi@200000' does not match '^([a-z][a-z0-9\\-]+-bus|bus|localbus|soc|axi|ahb|apb)(@.+)?$'
	from schema $id: http://devicetree.org/schemas/simple-bus.yaml#Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/nxp/imx/imx1.dtsi

@@ -68,7 +68,7 @@ soc {
 		interrupt-parent = <&aitc>;
 		ranges;
 
-		aipi@200000 {
+		bus@200000 {
 			compatible = "fsl,aipi-bus", "simple-bus";
 			#address-cells = <1>;
 			#size-cells = <1>;
@@ -155,7 +155,7 @@ uart3: serial@20a000 {
 			};
 		};
 
-		aipi@210000 {
+		bus@210000 {
 			compatible = "fsl,aipi-bus", "simple-bus";
 			#address-cells = <1>;
 			#size-cells = <1>;