[coreboot-gerrit] [M] Change in coreboot[main]: mb/dell: Convert E6400 into a variant

[Nicholas Chin (Code Review)]

Nicholas Chin has posted comments on this change by Nicholas Chin. ( https://review.coreboot.org/c/coreboot/+/84565?usp=email )

Change subject: mb/dell: Convert E6400 into a variant
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Set Ready For Review