Change in coreboot[master]: elog: Add a log for Chrome OS diagnostics boot in coreboot/bootmode

[Aaron Durbin (Code Review)]

Attention is currently required from: Hsuan Ting Chen, Hsuan-ting Chen, Paul Menzel.
Aaron Durbin has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/54948 )

Change subject: elog: Add a log for Chrome OS diagnostics boot in coreboot/bootmode
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Patch Set 1:

(2 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/54948/comment/196222cf_5dbb71d7 
PS1, Line 9: Add an elog type 0xb6 for Chrome OS diagnostics related events.
> The Chrome OS diagnostics is more like the fourth 'bootmode' of Chrome OS. […]

I think Paul was suggesting to also note that a log message is added as well.

Patchset:

PS1: 
src/security/vboot/bootmode.c: In function 'vboot_diagnostic_boot_requested':
src/security/vboot/bootmode.c:33:9: error: implicit declaration of function 'vb2api_diagnostic_boot_requested'; did you mean 'vboot_diagnostic_boot_requested'? [-Werror=implicit-function-declaration]
  return vb2api_diagnostic_boot_requested(vboot_get_context());
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
         vboot_diagnostic_boot_requested

You are going to need to update the vboot submodule pointer in a separate commit before this one or together.