ASoC: rockchip: i2s: configure the sdio pins' iomux mode

There are 3 i2s sdio pins, which iomux mode is as follows:

 - sdi3_sdo1
 - sdi2_sdo2
 - sdi1_sdo3

we need to configure these pins' iomux mode via the GRF register
when use multi channel playback/capture.

Signed-off-by: Sugar Zhang <sugar.zhang@rock-chips.com>
Signed-off-by: Mark Brown <broonie@kernel.org>