ufs: get rid of ->setattr() for symlinks

It was to needed for a couple of months in 2010, until UFS
quota support got dropped.  Since then it's equivalent to
simple_setattr() (i.e. the default) for everything except the
regular files.  And dropping it there allows to convert all
UFS symlinks to {page,simple}_symlink_inode_operations, getting
rid of fs/ufs/symlink.c completely.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>