[S] Change in coreboot[main]: {commonlib, libpayload}: Add "is external display" in coreboot table

[Yu-Ping Wu (Code Review)]

Attention is currently required from: Andrey Petrov, Arthur Heymans, Julius Werner, Karthik Ramasubramanian, Nick Vaccaro, Subrata Banik.

Yu-Ping Wu has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/77796?usp=email )

Change subject: {commonlib, libpayload}: Add "is_external display" in coreboot table
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Patch Set 4:

(2 comments)

File src/drivers/intel/fsp2_0/Kconfig:

https://review.coreboot.org/c/coreboot/+/77796/comment/8a916b4c_f64b7433 :
PS4, Line 447: config REPORT_EXTERNAL_DISPLAY_AT_PREBOOT
Is this used anywhere?

File src/drivers/intel/fsp2_0/include/fsp/graphics.h:

https://review.coreboot.org/c/coreboot/+/77796/comment/a405d2bf_6b7f2750 :
PS4, Line 25: int soc_report_external_display(void);
If it's declared here (only for intel fsp), then the function name should have the `fsp_` prefix. Otherwise, this should be declared in a general header file (shared for all platforms).