Add syscall setup to kstart_ap

src/arch/x86_64/start.rs

@@ -175,6 +175,9 @@ pub unsafe extern fn kstart_ap(args_ptr: *const KernelArgsAp) -> ! {
         // Set up IDT for AP
         idt::init_paging();
 
+        // Set up syscall instruction
+        interrupt::syscall::init();
+
         // Test tdata and tbss
         {
             assert_eq!(TBSS_TEST_ZERO, 0);