Latest change allowed to add dependency on NvVarStoreFormattedLib for the DXE_DRIVER modules. Although effectively it is hooked using the 'NULL' class, extend the LIBRARY_CLASS with according type for consistency sake. Signed-off-by: Marcin Wojtas <mw@semihalf.com> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>