devlink: add instance lock assertion in devl_is_registered()

After region and linecard lock removals, this helper is always supposed
to be called with instance lock held. So put the assertion here and
remove the comment which is no longer accurate.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/devlink/devl_internal.h

@@ -85,9 +85,7 @@ struct devlink *devlinks_xa_find_get(struct net *net, unsigned long *indexp);
 
 static inline bool devl_is_registered(struct devlink *devlink)
 {
-	/* To prevent races the caller must hold the instance lock
-	 * or another lock taken during unregistration.
-	 */
+	devl_assert_locked(devlink);
 	return xa_get_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
 }