libpayload: Some more compatibility (for flashrom)

libpayload: Some more compatibility (for flashrom)

libpci defines an arbitrary set of PCI vendor IDs, flashrom uses the
Intel definition. Add it.

flashrom also requires inttypes.h, so add the OpenBSD version

Change-Id: I9bffd8193f635c375ac4d6b6eae8d3d876b95f5f
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/154
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>