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>