meta-ohos-demo/layer.conf: Add Copyright and License for reuse compliance

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>

meta-ohos-demo/conf/layer.conf

+# SPDX-FileCopyrightText: Huawei Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+
 # We have a conf and classes directory, add to BBPATH
 BBPATH .= ":${LAYERDIR}"