fsp_srv: Remove unnecessary vector construction in IFile's Write() function

We can avoid constructing a std::vector here by simply passing a pointer
to the original data and the size of the copy we wish to perform to the
backend's Write() function instead, avoiding copying the data where it's
otherwise not needed.

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

@@ -149,8 +149,9 @@ private:
             length, data.size());
 
         // Write the data to the Storage backend
-        std::vector<u8> actual_data(data.begin(), data.begin() + length);
-        const std::size_t written = backend->WriteBytes(std::move(actual_data), offset);
+        const auto write_size =
+            static_cast<std::size_t>(std::distance(data.begin(), data.begin() + length));
+        const std::size_t written = backend->Write(data.data(), write_size, offset);
 
         ASSERT_MSG(static_cast<s64>(written) == length,
                    "Could not write all bytes to file (requested={:016X}, actual={:016X}).", length,