nvme: remove virtual boundary for sgl capable devices

The nvme virtual boundary is only required for the PRP format. Devices
that can use SGL for DMA don't need it for IO queues. Drop reporting it
for such devices; rdma fabrics controllers will continue to use the
limit as they currently don't report any boundary requirements, but tcp
and fc never needed it in the first place so they get to report no
virtual boundary.

Applications may continue to align to the same virtual boundaries for
optimization purposes if they want, and the driver will continue to
decide whether to use the PRP format the same as before if the IO allows
it.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/target/loop.c

@@ -511,6 +511,7 @@ static const struct nvme_ctrl_ops nvme_loop_ctrl_ops = {
 	.submit_async_event	= nvme_loop_submit_async_event,
 	.delete_ctrl		= nvme_loop_delete_ctrl_host,
 	.get_address		= nvmf_get_address,
+	.get_virt_boundary	= nvme_get_virt_boundary,
 };
 
 static int nvme_loop_create_io_queues(struct nvme_loop_ctrl *ctrl)