greybus: Revert "protocol.c: fix a kernel panic caused by __gb_protocol_register"

This reverts commit 57131bf309d34568dd3b8f8e9da7a7ba25e9495e, it isn't
going to be needed as the patch this fixes will be reverted.
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/protocol.c

@@ -70,7 +70,7 @@ int __gb_protocol_register(struct gb_protocol *protocol, struct module *module)
 	 * We need to insert the protocol here, before the existing one
 	 * (or before the head if we searched the whole list)
 	 */
-	list_add_tail(&protocol->links, &gb_protocols);
+	list_add_tail(&protocol->links, &existing->links);
 	spin_unlock_irq(&gb_protocols_lock);
 
 	pr_info("Registered %s protocol.\n", protocol->name);