Bit 3 in byte 31 of the Sixaxis report indicates whether the battery is
charging or not charging as opposed to whether or not the cable is plugged in.
As a result, when connected via USB and fully charged, the power_supply status
is wrongly reported as 'Discharging' instead of 'Full'.

Use the battery level value to set the cable state so that the power status
is reported correctly as that seems to be the only reliable way to determine the
cable status on the Sixaxis.
Signed-off-by: NFrank Praznik <frank.praznik@oh.rr.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>