[UDFS] Fix code used to get drive size to not cause the ATAPI driver to get involved when it fails to find a descriptor when mounting

The ATAPI driver's new code can be found in the master branch. It is being used by the official master branch in the repository at reactos/reactos. I am replacing the udfs driver's code in the clone I made of it with the one from the branch being used for Copilot to work on.