Allow detecting ACP6x DMIC via _DSD

Merge series from Mario Limonciello <mario.limonciello@amd.com>:

It's not possible to probe for the presence of a DMIC, so the ACP6x
machine driver currently has a hardcoded list of all the systems known
to have a DMIC connected to the ACP.

Although this design works it means that the acp6x driver needs to always
grow with more systems and worse, if an OEM introduces a new system there
will be a mismatch in time that even if the driver (otherwise) works fine
it needs their system added to the list to work.

So this series introduces a _DSD that OEMs can populate into the BIOS to
indicate presence of a DMIC.