udf: decrement correct link count in udf_rmdir

It appears that a minor thinko occurred in udf_rmdir and the
(already-cleared) link count on the directory that is being removed was
being decremented instead of the link count on its parent directory.  This
gives rise to lots of kernel messages similar to:

UDF-fs warning (device loop1): udf_rmdir: empty directory has nlink != 2 (8)

when removing directory trees.  No other ill effects have been observed but
I guess it could theoretically result in the link count overflowing on a
very long-lived, much modified directory.
Signed-off-by: Stephen Mollett <molletts@yahoo.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Jan Kara <jack@ucw.cz>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/udf/namei.c

@@ -878,7 +878,7 @@ static int udf_rmdir(struct inode * dir, struct dentry * dentry)
 			inode->i_nlink);
 	clear_nlink(inode);
 	inode->i_size = 0;
-	inode_dec_link_count(inode);
+	inode_dec_link_count(dir);
 	inode->i_ctime = dir->i_ctime = dir->i_mtime = current_fs_time(dir->i_sb);
 	mark_inode_dirty(dir);