ASoC: rk3308_codec: configure ADC/DAC flexibility on hw_params

We need to know how many channels that are needed
to enable on hw_params for ADC groups, it's more
reasonable and more flexible.

By the way, clean up some coding styles.

Change-Id: Ia13b1667492dd60a63fc17130ff09b6b1b01b8df
Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>

Author: acgzx