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>