crypto: cavium/nitrox - remove check of list iterator against head past the loop body

When list_for_each_entry() completes the iteration over the whole list
without breaking the loop, the iterator value will be a bogus pointer
computed based on the head element.

While it is safe to use the pointer to determine if it was computed
based on the head element, either with list_entry_is_head() or
&pos->member == head, using the iterator variable after the loop should
be avoided.

In preparation to limit the scope of a list iterator to the list
traversal loop, use a dedicated pointer to point to the found element [1].

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/cavium/nitrox/nitrox_main.c

@@ -269,15 +269,17 @@ static void nitrox_remove_from_devlist(struct nitrox_device *ndev)
 
 struct nitrox_device *nitrox_get_first_device(void)
 {
-	struct nitrox_device *ndev;
+	struct nitrox_device *ndev = NULL, *iter;
 
 	mutex_lock(&devlist_lock);
-	list_for_each_entry(ndev, &ndevlist, list) {
-		if (nitrox_ready(ndev))
+	list_for_each_entry(iter, &ndevlist, list) {
+		if (nitrox_ready(iter)) {
+			ndev = iter;
 			break;
+		}
 	}
 	mutex_unlock(&devlist_lock);
-	if (&ndev->list == &ndevlist)
+	if (!ndev)
 		return NULL;
 
 	refcount_inc(&ndev->refcnt);