[efi] Fix building with newer binutils

Newer versions of bfd.h require definitions for the PACKAGE and
PACKAGE_VERSION macros used by autotools.  Work around this by
manually defining these macros before including bfd.h.

Originally-fixed-by: Brandon Penglase <bpenglase-ipxe@spaceservices.net>
Tested-by: Brandon Penglase <bpenglase-ipxe@spaceservices.net>
Signed-off-by: Michael Brown <mcb30@ipxe.org>