x86, VisWS: turn into generic arch, enhance include/asm-x86/mach-default/smpboot_hooks.h

Allow the generic smpboot quirks code to be built with
ONFIG_X86_IO_APIC disabled. This way VISWS will be able
to use it as-is.

Signed-off-by: Ingo Molnar <mingo@elte.hu>