Kernel/Loader: Grab the system mode from the NCCH ExHeader.

3dsx and elf files default to system mode 2 (96MB allocated to the application).

This allows Home Menu to boot without modifications.
Closes #1849

src/core/hle/kernel/kernel.cpp

@@ -124,13 +124,11 @@ void HandleTable::Clear() {
 }
 
 /// Initialize the kernel
-void Init() {
+void Init(u32 system_mode) {
     ConfigMem::Init();
     SharedPage::Init();
 
-    // TODO(yuriks): The memory type parameter needs to be determined by the ExHeader field instead
-    // For now it defaults to the one with a largest allocation to the app
-    Kernel::MemoryInit(2); // Allocates 96MB to the application
+    Kernel::MemoryInit(system_mode);
 
     Kernel::ResourceLimitsInit();
     Kernel::ThreadingInit();