nvmet-fc: rename ls_list to ls_rcv_list

In preparation to add ls request support, rename the current ls_list,
which is RCV LS request only, to ls_rcv_list.

Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>