Reorder code to avoid multiple inclusion of elf.h.

#undef several symbols to avoid build errors over redefinitions.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>