Add thinkpad battery charge max (conservation mode)

[h00bi]

On may Thinkpads, there is no simple conservation mode, and no /sys/bus/platform/devices/VPC2004\

instead, battery limits are set like this:

/sys/class/power_supply/BAT0/charge_start_threshold = 75 [%]
/sys/class/power_supply/BAT0/charge_stop_threshold = 80 [%]

and

/sys/class/power_supply/BAT1/charge_start_threshold = 75 [%]
/sys/class/power_supply/BAT1/charge_stop_threshold = 80 [%]

would be great if you could implement these settings, since TLP has a huge load of settings and is much more complicated.