Btrfs: make error return negative in btrfs_sync_file()

It appears the error return should be negative

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index ae96fda..413a30d 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1133,7 +1133,7 @@
 	}
 	mutex_lock(&dentry->d_inode->i_mutex);
 out:
-	return ret > 0 ? EIO : ret;
+	return ret > 0 ? -EIO : ret;
 }
 
 static const struct vm_operations_struct btrfs_file_vm_ops = {