some monitors care about the parity bit in the sub-frame of I2S,
but the cdn-dp always set this bit to "1", so these monitors
do not have sound output if use i2s, use spdif can fix this issue.
Signed-off-by: NChris Zhong <zyw@rock-chips.com>
Signed-off-by: NLin Huang <hl@rock-chips.com>
Signed-off-by: NMark Brown <broonie@kernel.org>