x86: remove smpboot_32.c and smpboot_64.c

Remove the last leftovers from the files. Move the ones
that are still used to the files they belong, the others
that grep can't reach, simply throw away.

Merge comments ontop of file and that's it: smpboot integrated

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>