ASoC: rockchip-i2s: dt: swap tx and rx channed request number in example

Reference to RK3288 TRM, fix an error channel id for i2s tx and rx
Table 10-1 DMAC_BUS Request Mapping Table
Req number	Source	Polarity
0		I2S tx	High level
1		I2S rx	High level

Tested on RK3288 board.
Signed-off-by: Jianqun <jay.xu@rock-chips.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/rockchip-i2s.txt

@@ -31,7 +31,7 @@ i2s@ff890000 {
 	#address-cells = <1>;
 	#size-cells = <0>;
 	dmas = <&pdma1 0>, <&pdma1 1>;
-	dma-names = "rx", "tx";
+	dma-names = "tx", "rx";
 	clock-names = "i2s_hclk", "i2s_clk";
 	clocks = <&cru HCLK_I2S0>, <&cru SCLK_I2S0>;
 };