staging: exfat: Collapse redundant return code translations

Now that we no longer use odd internal return codes, we can
heave the translation code over the side, and just pass the
error code back up the call chain.

Signed-off-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Link: https://lore.kernel.org/r/20191112021000.42091-9-Valdis.Kletnieks@vt.edu


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>