IEC60958-1, and AES-3 formats.
- tdm-slots : Slots for TDM operation. Indicates number of channels transmitted
or received over one serializer.
-- num-serializer : Serializers used by McASP.
- serial-dir : A list of serializer configuration. Each entry is a number
indication for serializer pin direction.
(0 - INACTIVE, 1 - TX, 2 - RX)