Support virt armv8.(Todo: fix clock intr)

Ubiquitous/XiZi_AIoT/softkernel/task/memspace.c

@@ -127,6 +127,7 @@ uintptr_t* load_memspace(struct MemSpace* pmemspace, char* img_start)
         // 1. alloc space
         if ((load_size = xizi_pager.resize_user_pgdir(&pgdir, load_size, ph.vaddr + ph.memsz))
             != ph.vaddr + ph.memsz) {
+            ERROR("Add uspace size failed.\n");
             goto error_exec;
         }
         // 2. copy inode to space

Ubiquitous/XiZi_AIoT/softkernel/task/schedule.c

@@ -42,6 +42,7 @@ struct Thread* max_priority_runnable_task(void)
 
     DOUBLE_LIST_FOR_EACH_ENTRY(task, &xizi_task_manager.task_list_head[priority], node)
     {
+        assert(task != NULL);
         if (task->state == READY && !task->dead) {
             // found a runnable task, stop this look up
             return task;