meta-ohos-demo: Add layer for compatibility

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
+
+# This layer was deprecated in favour of meta-ohos-blueprints. This is a
+# compatible layer to not break existing bblayers.conf.
+BBPATH .= ":${LAYERDIR}/../meta-ohos-blueprints"
+
+# We have recipes-* directories, add to BBFILES
+BBFILES += "${LAYERDIR}/../meta-ohos-blueprints/recipes-*/*/*.bb \
+            ${LAYERDIR}/../meta-ohos-blueprints/recipes-*/*/*.bbappend"
+
+BBFILE_COLLECTIONS += "meta-ohos-demo"
+BBFILE_PATTERN_meta-ohos-demo = "^${LAYERDIR}/../meta-ohos-blueprints"
+BBFILE_PRIORITY_meta-ohos-demo = "6"
+
+LAYERDEPENDS_meta-ohos-demo = "core"
+LAYERSERIES_COMPAT_meta-ohos-demo = "dunfell"