[coreboot] simplest fmap for minimal vboot deployment

[Persmule]

Hi all,
I found the typical fmap for a coreboot build using vboot (e.g. those for chromeos) is quite complex, at least with two RW sections containing CBFS, but I only want to use vboot to perform TPM measurement (like what head does with a patched coreboot), so

the simple scheme with a single CBFS containing all stages and payloads is prefered.

My question is: if vboot is only used to perform TPM measurement, at least which sections must be added to the fmap, in addition to default ones (RW_MRC_CACHE and CBFS), allowing vboot to work?