power: generic-adc-battery: check for duplicate properties copied from iio channels

power: generic-adc-battery: check for duplicate properties copied from iio channels

BugLink: https://bugs.launchpad.net/bugs/1835972
commit a427503edaaed9b75ed9746a654cece7e93e60a8 upstream.

If an iio channel defines a basic property, there are duplicate entries
in /sys/class/power/*/uevent.

So add a check to avoid duplicates. Since all channels may be duplicates,
we have to modify the related error check.

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Cc: stable@vger.kernel.org
Fixes: e60fea794e6e ("power: battery: Generic battery driver using IIO")
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>