modpost: remove unneeded local variable in contains_namespace()

The local variable, ns_entry, is unneeded.

While I was here, I also cleaned up the comparison with NULL or 0.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Matthias Maennich <maennich@google.com>

scripts/mod/modpost.c

@@ -239,10 +239,8 @@ static struct symbol *find_symbol(const char *name)
 static bool contains_namespace(struct namespace_list *list,
 			       const char *namespace)
 {
-	struct namespace_list *ns_entry;
-
-	for (ns_entry = list; ns_entry != NULL; ns_entry = ns_entry->next)
-		if (strcmp(ns_entry->namespace, namespace) == 0)
+	for (; list; list = list->next)
+		if (!strcmp(list->namespace, namespace))
 			return true;
 
 	return false;