Unused now.

Fixes: 4f1a22ee ("libata: Improve ATA queued command allocation")
Cc: John Garry <john.garry@huawei.com>
Signed-off-by: NHannes Reinecke <hare@suse.de>
Reviewed-by: NJohn Garry <john.garry@huawei.com>
Signed-off-by: NDamien Le Moal <damien.lemoal@opensource.wdc.com>