x86, VisWS: turn into generic arch, eliminate include/asm-x86/mach-visws/mach_apic.h

now that include/asm-x86/mach-visws/mach_apic.h equals
to include/asm-x86/mach-default/mach_apic.h, simply start
using the generic one.

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