[XS] Change in coreboot[main]: mb/google/fatcat: Add FW_CONFIG Support for ALC721 soundwire

[Naveen M (Code Review)]

Attention is currently required from: Anil Kumar K, Pranava Y N, Subrata Banik, Varun Upadhyay.

Naveen M has posted comments on this change by Varun Upadhyay. ( https://review.coreboot.org/c/coreboot/+/85074?usp=email )

Change subject: mb/google/fatcat: Add FW_CONFIG Support for ALC721 soundwire
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Patch Set 2:

(1 comment)

File src/mainboard/google/fatcat/variants/fatcat/overridetree.cb:

https://review.coreboot.org/c/coreboot/+/85074/comment/5c612897_0bd9d1ce?usp... :
PS2, Line 8: AUDIO_ALC721_SNDW
> > Yes. This data is important for kernel & ucm. […]

Re#1: In the current scenario yes, either RT721/RT722 will configure the same sdw GPIO pins.. But assume if we have multiple combinations for the same sound card but for different boards.

Example: Already Implemented following REX audio configuration caters different mic configuration for the same audio card(sof-rt5682) with delta wrt only DMIC channels, this helps us to apply different UCM settings by creating 2 folders(sof-rt5682.rex & sof-rt5682.rex.2ch)

2channel dmic: https://chrome-internal.googlesource.com/chromeos/project/rex/rex/+/refs/hea... 
Corresponding UCM Directory: https://source.chromium.org/chromiumos/chromiumos/codesearch/+/e0fb79aeb6cce...

4channel dmic: https://chrome-internal.googlesource.com/chromeos/project/rex/rex/+/refs/hea...
Corresponding UCM Directory: https://source.chromium.org/chromiumos/chromiumos/codesearch/+/e0fb79aeb6cce...

Overall to distinguish UCM configuration for a specific board, currently we need to rely on cbi config.

Re#2,Re#3: As this method is already implemented in Rex, we followed a similar configuration, will explore better method if we can optimize this. Thanks