Add SDCA DisCo parsing support

Merge series from Charles Keepax <ckeepax@opensource.cirrus.com>:

The MIPI SoundWire Device Class for Audio (SDCA) specification defines
most details of the hardware in ACPI using the MIPI Discovery and
Configuration (DisCo) specification. This patch chain adds support for
parsing most of this information into the kernel such that future work
can make use of it to construct CODEC devices and soundcards.

The most notable outstanding work here, is parsing the separate
properties for the Control Numbers (roughly equivalent to channels)
within an individual Control. The separate Control Numbers are
supported but currently only the scheme were a single default etc. is
supplied for all.  This should not be super hard to add in the future
but isn't currently required by any of the hardware I am working to
support.