Merge pull request #789 from junbo42/linux-timers-3-fix

cpu_idle_loop logical in book is wrong

Timers/linux-timers-3.md

@@ -61,6 +61,7 @@ static void cpu_idle_loop(void)
 		...
 		...
 		schedule_preempt_disabled();
+	}
 }
 ```
 

contributors.md

@@ -134,5 +134,6 @@ Thank you to all contributors:
 * [Yuxin Wu](https://github.com/chaffz)
 * [Biao Ding](https://github.com/SmallPond)
 * [Arfy slowy](https://github.com/slowy07)
+* [Junbo Jiang](https://github.com/junbo42)
 * [Dexter Plameras](https://github.com/dexterp)
 * [Jun Duan](https://github.com/waltforme)