service: Add pm services

Adds the skeleton for the process management services based off
information on Switch Brew.

src/core/hle/service/pm/pm.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::PM {
+
+/// Registers all PM services with the specified service manager.
+void InstallInterfaces(SM::ServiceManager& service_manager);
+
+} // namespace Service::PM