[coreboot] [PATCH]libpayload: implement libpci interface

[Patrick Georgi]

Hi,

attached patch provides a libpci implementation sufficient to get
flashrom to compile. It should work but is untested beyond what flashrom
does. It's also incomplete: libpci has many more capabilities than
exposed in this variant.

No pciutils code was harmed in its production - this code was written by
looking at flashrom's expectations, so licensing is clean.

Signed-off-by: Patrick Georgi