[coreboot] coreinfo: Add "submenus"

[Jordan Crouse]

We are adding stuff to coreinfo at a great rate.  We're going to run
out of space in the "menu" at the bottom, so this patch adds submenus
to categorize the individual modules.

Note - I am not a UI person - coreinfo probably represents the prettiest
thing I have ever coded, and thats sad.  So if anybody can think of a
cleaner and more sane way to present the information then we have now,
please do it.

Jordan