Add discovery flow remark by default

[bramstroker]

For device types smart_dimmer and smart_switch we can display a message in the discovery flow, when only_self_usage flag is not set or false.
In this scenario's the user can provide the linear or fixed power values for the connected appliance. So would be nice to explain that some more.

Something like:

This device controls a non-smart device, hence it only tracks standby power by default. You need to configure the power draw of the controlled device yourself while or after the configuring process.