Kernel: Move Aarch64 MMU debug message into memory manager initializer

Doing so unifies startup debug messages visually.

Kernel/Arch/aarch64/init.cpp

@@ -171,7 +171,6 @@ extern "C" [[noreturn]] void init()
 
     dmesgln("Starting SerenityOS...");
 
-    dmesgln("Initialize MMU");
     Memory::MemoryManager::initialize(0);
     DeviceManagement::initialize();
     SysFSComponentRegistry::initialize();

Kernel/Memory/MemoryManager.cpp

@@ -651,6 +651,7 @@ void MemoryManager::release_pte(PageDirectory& page_directory, VirtualAddress va
 
 UNMAP_AFTER_INIT void MemoryManager::initialize(u32 cpu)
 {
+    dmesgln("Initialize MMU");
     ProcessorSpecific<MemoryManagerData>::initialize();
 
     if (cpu == 0) {