ASoC: fsl_sai: add several improvements

Merge series from Shengjiu Wang <shengjiu.wang@nxp.com>:

Add several improvements for the sai interface.
1.allow to set mclk rate with zero clk_id for master mode
2.add xlate_tdm_slot_mask() callback to avoid channel constrain
3.separate 'is_dsp_mode' for tx and rx
4.separate set_tdm_slot() for tx and rx