Fix cloning meta-homeassistant and meta-oniro-blueprints-core

After performing layer cloning as it is described in README.md, both meta-oniro-homeassistant and meta-blueprints-core directories are empty, so it's not possible to add them as layers.

I think that adding --recursive is enough, like:

git clone --recursive https://gitlab.eclipse.org/eclipse/oniro-blueprints/energy-gateway/meta-oniro-blueprints-energy-gateway.git ~/oniroproject/meta-oniro-blueprints-energy-gateway`