[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>

src/util/elf2efi.c

  */
 
 #define _GNU_SOURCE
+#define PACKAGE "elf2efi"
+#define PACKAGE_VERSION "1"
 #include <stdint.h>
 #include <stddef.h>
 #include <stdlib.h>