cramfs_lookup(): use d_splice_alias()

simpler code that way, actually
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/cramfs/inode.c

@@ -808,10 +808,7 @@ static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, un
 	}
 out:
 	mutex_unlock(&read_mutex);
-	if (IS_ERR(inode))
-		return ERR_CAST(inode);
-	d_add(dentry, inode);
-	return NULL;
+	return d_splice_alias(inode, dentry);
 }
 
 static int cramfs_readpage(struct file *file, struct page *page)