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

[Angel Pons (Code Review)]

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

Change subject: drivers/efi: Add EFI variable store option support
......................................................................

Patch Set 12: Code-Review+1

(2 comments)

File tests/drivers/efivars.c:

https://review.coreboot.org/c/coreboot/+/52564/comment/b24a0fc7_f4572f5b 
PS10, Line 11: 	/* Firmware volume */
             : 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
             : 	0x00, 0x00, 0x8d, 0x2b, 0xf1, 0xff, 0x96, 0x76, 0x8b, 0x4c, 0xa9, 0x85, 0x27, 0x47,
             : 	0x07, 0x5b, 0x4f, 0x50, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x5f, 0x46,
             : 	0x56, 0x48, 0x36, 0x0e, 0x00, 0x00, 0x48, 0x00, 0x00, 0xfa, 0x00, 0x00, 0x00, 0x02,
             : 	0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
             : 	0x00, 0x00,
             : 	/* Variable Info Header */
             : 	0x78, 0x2c, 0xf3, 0xaa, 0x7b, 0x94, 0x9a, 0x43, 0xa1, 0x80, 0x2e, 0x14, 0x4e, 0xc3,
             : 	0x77, 0x92, 0xb8, 0xff, 0x00, 0x00, 0x5a, 0xfe, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
             : 	/* First entry: coreboot, data: "is great" */
             : 	0xaa, 0x55, 0x3f, 0xff, 0x07, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
             : 	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
             : 	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x12, 0x00, 0x00, 0x00, 0x09, 0x00,
             : 	0x00, 0x00, 0x1d, 0x4c, 0xae, 0xce, 0x5b, 0x33, 0x85, 0x46, 0xa4, 0xa0, 0xfc, 0x4a,
             : 	0x94, 0xee, 0xa0, 0x85, 0x63, 0x00, 0x6f, 0x00, 0x72, 0x00, 0x65, 0x00, 0x62, 0x00,
             : 	0x6f, 0x00, 0x6f, 0x00, 0x74, 0x00, 0x00, 0x00, 0x69, 0x73, 0x20, 0x67, 0x72, 0x65,
             : 	0x61, 0x74, 0x00,
> nit: Can you make it more descriptive?

I guess one could use a struct, but it might cause endianness issues.

File tests/drivers/efivars.c:

https://review.coreboot.org/c/coreboot/+/52564/comment/5709fdeb_884cc4a5 
PS12, Line 117: "is awesome"
Idea: store this in an array to avoid repeating it four times?