fixing init #9 link

Initialization/README.md

@@ -12,5 +12,5 @@ You will find here a couple of posts which describe the full cycle of kernel ini
 * [Architecture-specific initializations, again...](https://github.com/0xAX/linux-insides/blob/master/Initialization/linux-initialization-6.md) - describes continue of the architecture-specific initialization process.
 * [The End of the architecture-specific initializations, almost...](https://github.com/0xAX/linux-insides/blob/master/Initialization/linux-initialization-7.md) - describes the end of the `setup_arch` related stuff.
 * [Scheduler initialization](https://github.com/0xAX/linux-insides/blob/master/Initialization/linux-initialization-8.md) - describes preparation before scheduler initialization and initialization of it.
-* [RCU initialization](https://github.com/0xAX/linux-insides/blob/master/Initialization/linux-initialization-9.mdd) - describes the initialization of the [RCU](http://en.wikipedia.org/wiki/Read-copy-update).
+* [RCU initialization](https://github.com/0xAX/linux-insides/blob/master/Initialization/linux-initialization-9.md) - describes the initialization of the [RCU](http://en.wikipedia.org/wiki/Read-copy-update).
 * [End of the initialization](https://github.com/0xAX/linux-insides/blob/master/Initialization/linux-initialization-10.md) - the last part about linux kernel initialization.