btrfs: drop unused argument from extent_io_tree_init

all callers pass GFP_NOFS, but the GFP mask argument is not used in the
function; GFP_ATOMIC is passed to radix tree initialization and it's the
only correct one, since we're using the preload/insert mechanism of
radix tree.
Let's drop the gfp mask from btrfs function, this will not change
behaviour.

Signed-off-by: David Sterba <dsterba@suse.cz>
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index c571734..955f76e 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -80,8 +80,7 @@
 		INIT_LIST_HEAD(&cur_trans->pending_snapshots);
 		list_add_tail(&cur_trans->list, &root->fs_info->trans_list);
 		extent_io_tree_init(&cur_trans->dirty_pages,
-				     root->fs_info->btree_inode->i_mapping,
-				     GFP_NOFS);
+				     root->fs_info->btree_inode->i_mapping);
 		spin_lock(&root->fs_info->new_trans_lock);
 		root->fs_info->running_transaction = cur_trans;
 		spin_unlock(&root->fs_info->new_trans_lock);