add CPU affinity function

- syscall support
-- sched_setaffinity
-- sched_getaffinity
- migration in scheduler
- resched at return of syscalls/interrupts

kernel/mem.c

@@ -248,6 +248,7 @@ out:
 	dkprintf("[%d]page_fault_handler(%p,%lx,%p): (%d)\n",
 			ihk_mc_get_processor_id(), fault_addr, reason,
 			regs, error);
+	check_need_resched();
 	return;
 }