btrfs: btrfs_abort_transaction, drop root parameter

__btrfs_abort_transaction doesn't use its root parameter except to
obtain an fs_info pointer.  We can obtain that from trans->root->fs_info
for now and from trans->fs_info in a later patch.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/file-item.c

@@ -698,7 +698,7 @@ int btrfs_del_csums(struct btrfs_trans_handle *trans,
 			 */
 			ret = btrfs_split_item(trans, root, path, &key, offset);
 			if (ret && ret != -EAGAIN) {
-				btrfs_abort_transaction(trans, root, ret);
+				btrfs_abort_transaction(trans, ret);
 				goto out;
 			}