Let ifmgmt.c take care of calling efree(), since it's the once which
took out the contract to eventually call efree() when it called fetch().
Maintain the most recently loaded image at the start of the list, so that
imgautoselect() will pick it.
Strip down i386 PCI configuration space I/O to the bare minimum. A
typical build will now include 880 bytes of PCI support code, compared to
2327 bytes in Etherboot 5.4.
(There is a slight cost of around 5 extra bytes per access to a
non-constant config space address; this should be an overall win.
Driver-specific accesses will usually be to constant addresses, for
which there is no additional cost.)