Linux implementation should ignore portable devices

[svartalf]

Devices with scope != System should be ignored, since it is impossible to expect from drivers to provide the same amount of information as in case of system batteries.

scope attribute was introduced in this patch: http://lkml.iu.edu/hypermail/linux/kernel/1112.0/03454.html

Example of the battery report from the connected mice, reported by @o10g:

/sys/class/power_supply/hidpp_battery_0/capacity_level:Normal
/sys/class/power_supply/hidpp_battery_0/manufacturer:Logitech
/sys/class/power_supply/hidpp_battery_0/model_name:Marathon Mouse/Performance Plus M705
/sys/class/power_supply/hidpp_battery_0/online:1
/sys/class/power_supply/hidpp_battery_0/scope:Device
/sys/class/power_supply/hidpp_battery_0/serial_number:406d-25-5b-d8-be
/sys/class/power_supply/hidpp_battery_0/status:Discharging
/sys/class/power_supply/hidpp_battery_0/type:Battery
/sys/class/power_supply/hidpp_battery_0/uevent:POWER_SUPPLY_NAME=hidpp_battery_0
/sys/class/power_supply/hidpp_battery_0/uevent:POWER_SUPPLY_ONLINE=1
/sys/class/power_supply/hidpp_battery_0/uevent:POWER_SUPPLY_STATUS=Discharging
/sys/class/power_supply/hidpp_battery_0/uevent:POWER_SUPPLY_SCOPE=Device
/sys/class/power_supply/hidpp_battery_0/uevent:POWER_SUPPLY_MODEL_NAME=Marathon Mouse/Performance Plus M705
/sys/class/power_supply/hidpp_battery_0/uevent:POWER_SUPPLY_MANUFACTURER=Logitech
/sys/class/power_supply/hidpp_battery_0/uevent:POWER_SUPPLY_SERIAL_NUMBER=406d-25-5b-d8-be
/sys/class/power_supply/hidpp_battery_0/uevent:POWER_SUPPLY_CAPACITY_LEVEL=Normal

[svartalf]

Fixed at e77b75880073fde663f56a9067de38b9207ee51f, issue close is postponed until next release.