clk: rockchip: rename the clk id for HCLK_I2S1_2CH

i2s1 has 2 channels but not 8 channels.

Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Signed-off-by: Andy Yan <andy.yan@rock-chips.com>

[and the clock id hasn't been used in either clock-driver nor dts,
 so is safe to rename]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>