netdevsim: dev: Fix memory leak in nsim_dev_take_snapshot_write

In case memory resources for dummy_data were allocated, release them
before return.

Addresses-Coverity-ID: 1491997 ("Resource leak")
Fixes: 7ef19d3b ("devlink: report error once U32_MAX snapshot ids have been used")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/netdevsim/dev.c

@@ -75,6 +75,7 @@ static ssize_t nsim_dev_take_snapshot_write(struct file *file,
 	err = devlink_region_snapshot_id_get(devlink, &id);
 	if (err) {
 		pr_err("Failed to get snapshot id\n");
+		kfree(dummy_data);
 		return err;
 	}
 	err = devlink_region_snapshot_create(nsim_dev->dummy_region,