Btrfs: stop passing a trans handle all around the reservation code

The only thing that we need to have a trans handle for is in
reserve_metadata_bytes and thats to know how much flushing we can do.  So
instead of passing it around, just check current->journal_info for a
trans_handle so we know if we can commit a transaction to try and free up space
or not.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 3bde17f..ffc42ef 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -197,9 +197,7 @@
 
 	rsv = trans->block_rsv;
 	trans->block_rsv = root->orphan_block_rsv;
-	ret = btrfs_block_rsv_check(trans, root,
-				    root->orphan_block_rsv,
-				    0, 5, 0);
+	ret = btrfs_block_rsv_check(root, root->orphan_block_rsv, 0, 5, 0);
 	if (ret)
 		return ret;