Change in coreboot[master]: mb/google/volteer: Create APIs for USB-C DP alternate mode support

[Curtis Chen (Code Review)]

Attention is currently required from: Furquan Shaikh, Tim Wawrzynczak, Zhuohao Lee, Derek Huang, Brandon Breitenstein, Curtis Chen.
Curtis Chen has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/57139 )

Change subject: mb/google/volteer: Create APIs for USB-C DP alternate mode support
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Patch Set 9:

(1 comment)

File src/soc/intel/common/block/tcss/tcss.c:

https://review.coreboot.org/c/coreboot/+/57139/comment/e3897858_9ad16c34 
PS9, Line 296: WAIT_FOR_DISPLAYPORT_TIMEOUT
> Does the waiting have to be done serially? can it be done in parallel?

Yes, we have a draft idea at my 8/26 comment.
The wait could be done in parallel.

Also, not sure google needs to support 2 output or not.
If yes,
in google_chromeec_pd_get_amode(uint16_t svid) 
we could use "ret |= 1 << i" rather than return directly.
(Based on my 8/26 comment)