i2c-for-6.8-rc1-rebased

(controllers set the flag, but there is no client to use it). Also,
CLASS_SPD support gets simplified to prepare removal in the future.
Class based instantiation is not recommended these days anyhow.
Furthermore, I2C core now creates a debugfs directory per I2C adapter.
Current bus driver users were converted to use it. Then, there are also
quite some driver updates. Standing out are patches for the wmt-driver
which is refactored to support more variants. This is the rebased pull
request where a large series for the designware driver was dropped.