x86: make native_machine_shutdown non-static

it will allow external users to call it. It is mainly
useful for routines that will override its machine_ops
field for its own special purposes, but want to call the
normal shutdown routine after they're done

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/include/asm-x86/reboot.h b/include/asm-x86/reboot.h
index 0891a41..e63741f 100644
--- a/include/asm-x86/reboot.h
+++ b/include/asm-x86/reboot.h
@@ -16,5 +16,6 @@
 
 void machine_real_restart(unsigned char *code, int length);
 void native_machine_crash_shutdown(struct pt_regs *regs);
+void native_machine_shutdown(void);
 
 #endif	/* _ASM_REBOOT_H */