nvmet: fix a memory leak

We forgot to free new_model_number

Fixes: 013b7ebe5a ("nvmet: make ctrl model configurable")
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/target/configfs.c

@@ -1136,6 +1136,7 @@ static ssize_t nvmet_subsys_attr_model_store(struct config_item *item,
 	up_write(&nvmet_config_sem);
 
 	kfree_rcu(new_model, rcuhead);
+	kfree(new_model_number);
 
 	return count;
 }