[coreboot] PCIe config and MMCONF

[Carl-Daniel Hailfinger]

MMCONF and PCIe BAR is a concept which has many different names in our
tree. It's almost impossible to find all code concerning MMCONFIG when
there are some hardcoded values and three different names for it.

MMCONF_BASE_ADDRESS, EXT_CONF_BASE_ADDRESS and DEFAULT_PCIEXBAR have the
same purpose. There are various places in the tree where that stuff is
hardcoded as 0xe0000000 or 0xf0000000 or 0xf4000000. Try grepping for
them. Bring antacid for your stomach.

Of course, that leads to bugs which are difficult to track down.

We need exactly one variable for the base address and another one for
the size of that area.

Ideas about the name?

Regards,
Carl-Daniel