TDM slot:

This specifies audio DAI's TDM slot.

TDM slot properties:
dai-tdm-slot-num : Number of slots in use.
dai-tdm-slot-width : Width in bits for each slot.
dai-tdm-slot-tx-mask : Transmit direction slot mask, optional
dai-tdm-slot-rx-mask : Receive direction slot mask, optional

For instance:
	dai-tdm-slot-num = <2>;
	dai-tdm-slot-width = <8>;
	dai-tdm-slot-tx-mask = <0 1>;
	dai-tdm-slot-rx-mask = <1 0>;

And for each spcified driver, there could be one .of_xlate_tdm_slot_mask()
to specify a explicit mapping of the channels and the slots. If it's absent
the default snd_soc_of_xlate_tdm_slot_mask() will be used to generating the
tx and rx masks.

For snd_soc_of_xlate_tdm_slot_mask(), the tx and rx masks will use a 1 bit
for an active slot as default, and the default active bits are at the LSB of
the masks.

The explicit masks are given as array of integers, where the first
number presents bit-0 (LSB), second presents bit-1, etc. Any non zero
number is considered 1 and 0 is 0. snd_soc_of_xlate_tdm_slot_mask()
does not do anything, if either mask is set non zero value.
