udf: fix ioctl errors

Currently, lsattr for instance in udf directory gives
"udf: Invalid argument While reading flags on ..."

This patch returns -ENOIOCTLCMD
when command is unknown to have more accurate message like this:
"Inappropriate ioctl for device While reading flags on ..."

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jan Kara <jack@suse.cz>