btrfs: drop unused parameter from btrfs_release_path

parameter tree root it's not used since commit
5f39d397df ("Btrfs: Create extent_buffer
interface for large blocksizes")

Signed-off-by: David Sterba <dsterba@suse.cz>

fs/btrfs/dir-item.c

@@ -172,7 +172,7 @@ second_insert:
 		ret = 0;
 		goto out_free;
 	}
-	btrfs_release_path(root, path);
+	btrfs_release_path(path);
 
 	btrfs_set_key_type(&key, BTRFS_DIR_INDEX_KEY);
 	key.offset = index;