service/fsp_srv: Remove unnecessary unknown member in OpenSaveDataFileSystem

The unknown member here is actually padding due to being passed as a
struct. We can do the same, and remove the need to pop a padding word.

src/core/hle/service/filesystem/fsp_srv.cpp

@@ -781,16 +781,17 @@ void FSP_SRV::CreateSaveDataFileSystem(Kernel::HLERequestContext& ctx) {
 }
 
 void FSP_SRV::OpenSaveDataFileSystem(Kernel::HLERequestContext& ctx) {
-    IPC::RequestParser rp{ctx};
-
-    auto space_id = rp.PopRaw<FileSys::SaveDataSpaceId>();
-    auto unk = rp.Pop<u32>();
-    LOG_INFO(Service_FS, "called with unknown={:08X}", unk);
+    LOG_INFO(Service_FS, "called.");
 
-    auto save_struct = rp.PopRaw<FileSys::SaveDataDescriptor>();
+    struct Parameters {
+        FileSys::SaveDataSpaceId save_data_space_id;
+        FileSys::SaveDataDescriptor descriptor;
+    };
 
-    auto dir = OpenSaveData(space_id, save_struct);
+    IPC::RequestParser rp{ctx};
+    const auto parameters = rp.PopRaw<Parameters>();
 
+    auto dir = OpenSaveData(parameters.save_data_space_id, parameters.descriptor);
     if (dir.Failed()) {
         IPC::ResponseBuilder rb{ctx, 2, 0, 0};
         rb.Push(FileSys::ERROR_ENTITY_NOT_FOUND);