locktorture: Check the correct variable for allocation failure

There is a typo so this checks the wrong variable.  "chains" plural vs
"chain" singular.  We already know that "chains" is non-zero.

Fixes: 7f99362 ("locktorture: Add call_rcu_chains module parameter")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

Author: Dan Carpenter

kernel/locking/locktorture.c

@@ -1075,7 +1075,7 @@ static int call_rcu_chain_init(void)
 	if (call_rcu_chains <= 0)
 		return 0;
 	call_rcu_chain = kcalloc(call_rcu_chains, sizeof(*call_rcu_chain), GFP_KERNEL);
-	if (!call_rcu_chains)
+	if (!call_rcu_chain)
 		return -ENOMEM;
 	for (i = 0; i < call_rcu_chains; i++) {
 		call_rcu_chain[i].crc_stop = false;