meta-ohos: Add meta-ohos-core to bblayers.conf.sample

Add meta-ohos-core to the sample list of layers being
used in the project.
The layer contains:
* Core elements of the OpenHarmony distribution
* Reference images recipes

Signed-off-by: Zbigniew Bodek <zbigniew.bodek@huawei.com>

flavours/linux/bblayers.conf.sample

@@ -9,6 +9,7 @@ BBLAYERS ?= " \
   ##OEROOT##/meta \
   ##OEROOT##/meta-poky \
   ##OEROOT##/meta-yocto-bsp \
+  ##OEROOT##/../meta-ohos/meta-ohos-core \
   ##OEROOT##/../meta-ohos/meta-ohos-foundation \
   ##OEROOT##/../meta-intel \
   ##OEROOT##/../meta-seco-intel \