service: Add ldr services

Adds the skeleton for the ldr-related services based off the information
provided on Switch Brew.

src/core/hle/service/ldr/ldr.h

@@ -0,0 +1,16 @@
+// Copyright 2018 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+namespace Service::SM {
+class ServiceManager;
+}
+
+namespace Service::LDR {
+
+/// Registers all LDR services with the specified service manager.
+void InstallInterfaces(SM::ServiceManager& sm);
+
+} // namespace Service::LDR