HID: logitech-hidpp: battery: provide CAPACITY property for newer devices

For devices that only support the BATTERY_VOLTAGE (0x1001) feature, UPower
requires the additional information provided by this patch, to set them up.

Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
Reviewed-by: Filipe Laíns <lains@riseup.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>