ARM: dts: imx50: Pass the 'dma-cells' property

Pass the '#dma-cells' property in the sdma node, so that the following
build warning is gone:

  DTC     arch/arm/boot/dts/imx50-evk.dtb
arch/arm/boot/dts/imx50-evk.dtb: Warning (dmas_property): Missing property '#dma-cells' in node /soc/aips@60000000/sdma@63fb0000 or bad phandle (referred from /soc/aips@50000000/spba@50000000/ssi@50014000:dmas[0])
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx50.dtsi

@@ -443,6 +443,7 @@ sdma: sdma@63fb0000 {
 				clocks = <&clks IMX5_CLK_SDMA_GATE>,
 					 <&clks IMX5_CLK_SDMA_GATE>;
 				clock-names = "ipg", "ahb";
+				#dma-cells = <3>;
 				fsl,sdma-ram-script-name = "imx/sdma/sdma-imx50.bin";
 			};