skylake: Add Audio DSP device

Add the Audio DSP device for skylake as a PCI driver with a static
scan_bus handler so generic devices can be declared under it.

This is for devices like the Maxim 98357A which is connected on the
I2S bus for data but has no control channel bus and instead just has
a GPIO for channel selection and power down control and needs to
describe that GPIO connection to the OS via ACPI.

Change-Id: Iae02132ff9c510562483108ab280323f78873afd
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/14993
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
3 files changed