networkmanager: Use a persistent mount point for system-connections

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>
Signed-off-by: Bernhard Rosenkraenzer <bernhard.rosenkraenzer.ext@huawei.com> [adapted to current meta-ohos]

meta-ohos-core/recipes-connectivity/networkmanager/networkmanager_%.bbappend

+# SPDX-FileCopyrightText: Huawei Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+inherit writables
+
+WRITABLES = "system-connections"
+WRITABLE_PATH[system-connections] = "/etc/NetworkManager/system-connections"