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

[Subrata Banik (Code Review)]

Attention is currently required from: Julius Werner, Nicholas Chin.

Subrata Banik has posted comments on this change by Nicholas Chin. ( https://review.coreboot.org/c/coreboot/+/85905?usp=email )

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

Patch Set 6:

(1 comment)

File src/drivers/option/Makefile.mk:

https://review.coreboot.org/c/coreboot/+/85905/comment/922a920c_e5e9b8a0?usp... :
PS6, Line 6: smm-$(CONFIG_USE_CBFS_FILE_OPTION_BACKEND) += cbfs_file_option.c
as we don't compile vboot library in smm mode, I'm getting compilation error due to undefined reference to `vb2_digest_size` and others

```
    HOSTCC     cbfstool/bpdt_1_7.o
    HOSTCC     cbfstool/subpart_hdr_1.o
/build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-sdk/bin/i386-elf-ld.bfd: /build/rex/tmp/portage/sys-boot/coreboot-9999/work/build/rex0/smm/commonlib/bsd/cbfs_private.o: in function `cbfs_file_hash':
/build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-9999/src/commonlib/bsd/cbfs_private.c:207: undefined reference to `vb2_digest_size'
    HOSTCC     cbfstool/subpart_hdr_2.o
    HOSTCC     cbfstool/subpart_entry_1.o
/build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-sdk/bin/i386-elf-ld.bfd: /build/rex/tmp/portage/sys-boot/coreboot-9999/work/build/rex0/smm/lib/cbfs.o: in function `vboot_hwcrypto_allowed':
/build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-9999/src/security/vboot/misc.h:98: undefined reference to `vboot_get_context'
/build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-sdk/bin/i386-elf-ld.bfd: /build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-9999/src/security/vboot/misc.h:98: undefined reference to `vb2api_hwcrypto_allowed'
/build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-sdk/bin/i386-elf-ld.bfd: /build/rex/tmp/portage/sys-boot/coreboot-9999/work/build/rex0/smm/lib/cbfs.o: in function `cbfs_file_hash_mismatch':
/build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-9999/src/lib/cbfs.c:177: undefined reference to `vb2_hash_verify'
/build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-sdk/bin/i386-elf-ld.bfd: /build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-9999/src/lib/cbfs.c:182: undefined reference to `vboot_get_context'
/build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-sdk/bin/i386-elf-ld.bfd: /build/rex/tmp/portage/sys-boot/coreboot-9999/work/coreboot-9999/src/lib/cbfs.c:182: undefined reference to `vboot_fail_and_reboot'
    OBJCOPY    bootblock.raw.bin
    HOSTCC     cbfstool/ifittool (link)
    HOSTCC     cbfstool/cse_fpt (link)
```

I believe we don't want to link `FWLIB = ${BUILD}/vboot_fw.a` in smm?

@[e-mail] thoughts ?