greybus: power_supply: fix unregister on error path

If setup fail the release for each supply needs to know the status at
unregister time. So, add the field to the structure, update it at setup
time and use it at release.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Reported-by: Johan Hovold <johan@hovoldconsulting.com>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>