delayacct: optimize delayacct init

In delayacct_init(), first there is no need to assign delayacct_on to
delayacct_on in set_delayacct(). Second if delayacct_on is 0, there
is no need call delayacct_tsk_init().

Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>

kernel/delayacct.c

@@ -39,8 +39,13 @@ __setup("delayacct", delayacct_setup_enable);
 void delayacct_init(void)
 {
 	delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC|SLAB_ACCOUNT);
+
+	if (delayacct_on)
+		static_branch_enable(&delayacct_key);
+	else
+		return;
+
 	delayacct_tsk_init(&init_task);
-	set_delayacct(delayacct_on);
 }
 
 #ifdef CONFIG_PROC_SYSCTL