ARM: dts: imx6sx: Fix SAI DMA index

According to sdma_peripheral_type in include/linux/platform_data/dma-imx.h
IMX_DMATYPE_SAI corresponds to index 24, so fix it accordingly.
Suggested-by: NZidan Wang <zidan.wang@nxp.com>
Signed-off-by: NFabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6sx.dtsi

@@ -970,7 +970,7 @@
 					 <&clks 0>, <&clks 0>;
 				clock-names = "bus", "mclk1", "mclk2", "mclk3";
 				dma-names = "rx", "tx";
-				dmas = <&sdma 31 23 0>, <&sdma 32 23 0>;
+				dmas = <&sdma 31 24 0>, <&sdma 32 24 0>;
 				dma-source = <&gpr 0 15 0 16>;
 				status = "disabled";
 			};
@@ -990,7 +990,7 @@
 					 <&clks 0>, <&clks 0>;
 				clock-names = "bus", "mclk1", "mclk2", "mclk3";
 				dma-names = "rx", "tx";
-				dmas = <&sdma 33 23 0>, <&sdma 34 23 0>;
+				dmas = <&sdma 33 24 0>, <&sdma 34 24 0>;
 				dma-source = <&gpr 0 17 0 18>;
 				status = "disabled";
 			};