[S] Change in coreboot[main]: drivers/option: Add CBFS file based option backend

[Nicholas Chin (Code Review)]

Attention is currently required from: Jérémy Compostella, Nicholas Chin, Subrata Banik.

Hello build bot (Jenkins),

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/85905?usp=email

to look at the new patch set (#11).

Change subject: drivers/option: Add CBFS file based option backend
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drivers/option: Add CBFS file based option backend

Add a new option backend that uses values stored in CBFS files, similar
to the SeaBIOS runtime config options stored in files with the etc/
prefix. Options should be stored in CBFS with the option/ prefix. Values
can be set using `cbfstool coreboot.rom add-int -n option/<option-name>
-i <value>`. For simplicity, options should be stored in the COREBOOT
(RO) FMAP region, which is the default for cbfstool. This backend is not
available in SMM due to cbfs dependencies on vboot functions which are
not added to SMM, and thus the fallback will be returned by calls to
get_uint_option() in SMM.

Tested with QEMU Q35 by setting various options for "sata_mode" and
observing the console output for the SATA controller mode during
i82801ix_sata initialization.

Change-Id: Ifc0439ee42f13f49ae54d4855d1d9333c39b01f5
Signed-off-by: Nicholas Chin 
---
M src/Kconfig
M src/drivers/option/Makefile.mk
A src/drivers/option/cbfs_file_option.c
M src/include/option.h
4 files changed, 47 insertions(+), 1 deletion(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/05/85905/11