x86: reboot.c declare port_cf9_safe before they get used

Impact: cleanup, avoid sparse warning

Include "../pci/pci.h" for port_cf9_safe

Fixes this sparse warning:

  arch/x86/kernel/reboot.c:43:6: warning: symbol 'port_cf9_safe' was not declared. Should it be static?
Signed-off-by: Jaswinder Singh <jaswinder@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/reboot.c

@@ -22,6 +22,7 @@
 #endif
 
 #include <mach_ipi.h>
+#include "../pci/pci.h"
 
 
 /*