nvme: open code nvme_put_ns_from_disk in nvme_ns_head_ctrl_ioctl

nvme_ns_head_ctrl_ioctl is always used on multipath nodes, so just call
srcu_read_unlock directly.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/host/ioctl.c

@@ -377,7 +377,7 @@ static int nvme_ns_head_ctrl_ioctl(struct nvme_ns *ns, unsigned int cmd,
 	int ret;
 
 	nvme_get_ctrl(ns->ctrl);
-	nvme_put_ns_from_disk(head, srcu_idx);
+	srcu_read_unlock(&head->srcu, srcu_idx);
 	ret = nvme_ctrl_ioctl(ns->ctrl, cmd, argp);
 
 	nvme_put_ctrl(ctrl);