ASoC: pcm3168a: Enable TDM support for DSP_A/B modes

The 24-bit TDM mode also applies to DSP_A and DSP_B modes.
Most dais on the SoC side can not interpret I2S/Left_j with other than 2
channels of audio.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>