fs-srv: GetFreeSpaceSize & GetTotalSpaceSize

Closes #3533

Turns out the functions were already implemented but just never added

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

@@ -316,8 +316,8 @@ public:
             {8, &IFileSystem::OpenFile, "OpenFile"},
             {9, &IFileSystem::OpenDirectory, "OpenDirectory"},
             {10, &IFileSystem::Commit, "Commit"},
-            {11, nullptr, "GetFreeSpaceSize"},
-            {12, nullptr, "GetTotalSpaceSize"},
+            {11, &IFileSystem::GetFreeSpaceSize, "GetFreeSpaceSize"},
+            {12, &IFileSystem::GetTotalSpaceSize, "GetTotalSpaceSize"},
             {13, &IFileSystem::CleanDirectoryRecursively, "CleanDirectoryRecursively"},
             {14, nullptr, "GetFileTimeStampRaw"},
             {15, nullptr, "QueryEntry"},