Currently, a not-yet-entirely-initialized battmgr (e.g. with pd-mapper
not having yet started or ADSP not being up etc.) results in a couple of
zombie power supply devices hanging around.

This is particularly noticeable when trying to suspend the device (even
s2idle): the PSY-internal thermal zone is inaccessible and returns
-ENODEV, which causes log spam.

Register the power supplies only after we received some notification
indicating battmgr is ready to take off.
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Tested-by: Luca Weiss <luca.weiss@fairphone.com>
Link: https://lore.kernel.org/r/20231218-topic-battmgr_fixture_attempt-v1-1-6145745f34fe@linaro.orgSigned-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>