[nrf fromlist] Bluetooth: mesh: update model extension

Adds a goto statement to ensure that model extensions are registered
in Composition Data Page 1 if it is enabled.

Upstream PR: zephyrproject-rtos/zephyr#64065
Signed-off-by: Håvard Reierstad <[email protected]>
(cherry picked from commit 24edc9d)

Author: HaavardRei

subsys/bluetooth/mesh/access.c

@@ -1678,7 +1678,7 @@ int bt_mesh_model_extend(struct bt_mesh_model *extending_mod, struct bt_mesh_mod
 	/* Check if a's list contains b */
 	for (it = a; (it != NULL) && (it->next != a); it = it->next) {
 		if (it == b) {
-			return 0;
+			goto register_extension;
 		}
 	}
 
@@ -1695,7 +1695,7 @@ int bt_mesh_model_extend(struct bt_mesh_model *extending_mod, struct bt_mesh_mod
 		a->next = b;
 	}
 
-
+register_extension:
 	if (IS_ENABLED(CONFIG_BT_MESH_COMP_PAGE_1)) {
 		return mod_rel_register(base_mod, extending_mod, RELATION_TYPE_EXT);
 	}