ARM: dts: imx23/28: Fix the DMA controller node name

Per fsl,mxs-dma.yaml, the node name should be 'dma-controller'.

Change it to fix the following dt-schema warning.

imx28-apf28.dtb: dma-apbx@80024000: $nodename:0: 'dma-apbx@80024000' does not match '^dma-controller(@.*)?$'
	from schema $id: http://devicetree.org/schemas/dma/fsl,mxs-dma.yaml#Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/nxp/mxs/imx23.dtsi

@@ -412,7 +412,7 @@ emi@80020000 {
 				status = "disabled";
 			};
 
-			dma_apbx: dma-apbx@80024000 {
+			dma_apbx: dma-controller@80024000 {
 				compatible = "fsl,imx23-dma-apbx";
 				reg = <0x80024000 0x2000>;
 				interrupts = <7>, <5>, <9>, <26>,

arch/arm/boot/dts/nxp/mxs/imx28.dtsi

@@ -990,7 +990,7 @@ etm: etm@80022000 {
 				status = "disabled";
 			};
 
-			dma_apbx: dma-apbx@80024000 {
+			dma_apbx: dma-controller@80024000 {
 				compatible = "fsl,imx28-dma-apbx";
 				reg = <0x80024000 0x2000>;
 				interrupts = <78>, <79>, <66>, <0>,