torture: Fix typo suppressing CPU-hotplug statistics

The torture status line contains a series of values preceded by "onoff:".
The last value in that line, the one preceding the "HZ=" string, is
always zero.  The reason that it is always zero is that torture_offline()
was incrementing the sum_offl pointer instead of the value that this
pointer referenced.  This commit therefore makes this increment operate
on the statistic rather than the pointer to the statistic.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/torture.c

@@ -117,7 +117,7 @@ bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
 				 torture_type, cpu);
 		(*n_offl_successes)++;
 		delta = jiffies - starttime;
-		sum_offl += delta;
+		*sum_offl += delta;
 		if (*min_offl < 0) {
 			*min_offl = delta;
 			*max_offl = delta;