udf: Some type fixes and cleanups

Make udf_check_valid() return 1 if the validity check passed and 0 otherwise.
So far it was the other way around which was a bit confusing. Also make
udf_vrs() return loff_t which is really the type it should return (not int).

Signed-off-by: Jan Kara <jack@suse.cz>

diff --cc fs/udf/super.c
Simple merge