Change in coreboot[master]: mb/google/volteer: Expand WP_RO region to 8MB in fmap

[Caveh Jalali (Code Review)]

Caveh Jalali has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/45889 )

Change subject: mb/google/volteer: Expand WP_RO region to 8MB in fmap
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Patch Set 2:
> Patch Set 2:
>
> 4 more MiB?? oh my... is that really the lowest resolution we can get away with?

FHD support apparently adds 4.5MiB and UHD would add 9.5MiB. i see some other
boards already increased WP_RO to 8MiB, so this is in line with those changes.
current rendering resolution for volteer specified in boards.yaml is 1200x675.

to put things into perspective, we can no longer build coreboot with USB_DEBUG
enabled in all the USB drivers due to the space crunch, so getting some headroom
back is a P0 to me.