core: hle: kernel: k_system_control: Add SecureAppletMemorySize.

src/core/hle/kernel/board/nintendo/nx/k_system_control.h

@@ -8,6 +8,10 @@
 namespace Kernel::Board::Nintendo::Nx {
 
 class KSystemControl {
+public:
+    // This can be overridden as needed.
+    static constexpr size_t SecureAppletMemorySize = 4 * 1024 * 1024; // 4_MB
+
 public:
     class Init {
     public: