intel_th: msu: Handle kstrndup() failure

Currently, the nr_pages attribute store does not check if kstrndup()
succeeded. Fix this.

Reported-by: Alan Cox <[e-mail]>
Signed-off-by: Alexander Shishkin <[e-mail]>
Reviewed-by: Laurent Fert <[e-mail]>

drivers/hwtracing/intel_th/msu.c

···
 	do {
 		end = memchr(p, ',', len);
 		s = kstrndup(p, end ? end - p : len, GFP_KERNEL);
+		if (!s) {
+			ret = -ENOMEM;
+			goto free_win;
+		}
+
 		ret = kstrtoul(s, 10, &val);
 		kfree(s);