NFS: use ERR_CAST()

Use ERR_CAST() intead of wierd-looking cast.
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/dir.c

@@ -1218,7 +1218,7 @@ static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, stru
 		goto out_unblock_sillyrename;
 	}
 	inode = nfs_fhget(dentry->d_sb, fhandle, fattr);
-	res = (struct dentry *)inode;
+	res = ERR_CAST(inode);
 	if (IS_ERR(res))
 		goto out_unblock_sillyrename;