Update SUMMARY.md

SUMMARY.md

@@ -28,14 +28,14 @@
     * [Initialization of external hardware interrupts structures](interrupts/interrupts-8.md)
     * [Softirq, Tasklets and Workqueues](interrupts/interrupts-9.md)
     * [Last part](interrupts/interrupts-10.md)
-* [Memory management](mm/README.md)
-    * [Memblock](mm/linux-mm-1.md)
-    * [Fixmaps and ioremap](mm/linux-mm-2.md)
 * [System calls](SysCall/README.md)
     * [Introduction to system calls](SysCall/syscall-1.md)
     * [How the Linux kernel handles a system call](SysCall/syscall-2.md)
     * [vsyscall and vDSO](SysCall/syscall-3.md)
     * [How the Linux kernel runs a program](SysCall/syscall-4.md)
+* [Memory management](mm/README.md)
+    * [Memblock](mm/linux-mm-1.md)
+    * [Fixmaps and ioremap](mm/linux-mm-2.md)
 * [SMP]()
 * [Concepts](Concepts/README.md)
     * [Per-CPU variables](Concepts/per-cpu.md)