Ulf Hansson [off-list ref] writes:

While adding devices to the generic PM domain we allocate data for the
struct generic_pm_domain_data.

Don't allow existing generic_pm_domain_data in this case, since that
indicates the device is already being added from another context. Let's
instead return an error.

Signed-off-by: Ulf Hansson <redacted>

Similar to PATCH 1/4, it would be good to summarize/remind why this
feature was added in the first place, and why it's not longer needed.

Kevin