x86: include mach_apic.h in smpboot_64.c and smpboot.c

After the inclusion, a lot of files needs fixing for conflicts,
some of them in the headers themselves, to accomodate for both
i386 and x86_64 versions.

[ mingo@elte.hu: build fix ]

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