In the next patch in the series, there will be the need to access the old
name, and its length, of an inode when logging the inode during a rename.
So instead of passing the inode to btrfs_log_new_name() pass the dentry,
because from the dentry we can get the inode, the name and its length.

This will avoid passing 3 new parameters to btrfs_log_new_name() in the
next patch - the name, its length and an index number. This way we end
up passing only 1 new parameter, the index number.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>