x86: vsmp_64 add missing includes

sparse mutters:
arch/x86/kernel/vsmp_64.c:126:5: warning: symbol 'is_vsmp_box' was not declared. Should it be static?
arch/x86/kernel/vsmp_64.c:145:13: warning: symbol 'vsmp_init' was not declared. Should it be static?

Include the appropriate headers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>