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

now that include/asm-x86/mach-visws/smpboot_hooks.h equals
to the default file in ../mach-default/smpboot_hooks.h, simply
include it instead of maintaining a copy.

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