Change in coreboot[master]: drivers/efi: Add EFI variable store option support

[Patrick Rudolph (Code Review)]

Attention is currently required from: Sean Rhodes, Martin Roth, Jakub Czapiga, Matt DeVillier, Angel Pons, Arthur Heymans, Patrick Rudolph.
Patrick Rudolph has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/52564 )

Change subject: drivers/efi: Add EFI variable store option support
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Patch Set 12:

(1 comment)

File src/drivers/efi/efivars.c:

https://review.coreboot.org/c/coreboot/+/52564/comment/36df85d7_ea4b616c 
PS12, Line 48: c < 0x80
> Isn't char16 is signed? How does this work with negative numbers?

UEFI is weird. Char16 is actually unsigned:

typedef unsigned short      CHAR16;