isofs: convert isofs to use the new mount API

This also renames iso9660_options to isofs_options, for
consistency.

Signed-off-by: Eric Sandeen <[email protected]>
cc: Jan Kara <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Message-Id: <[email protected]>

Author: Eric Sandeen