This works for me BUT you need to make sure the three definitions are on a new line. So the file /etc/udev/rules.d/99-devterm-charging.rules should look like this. Then, after a reboot my amps went from 0,7A to almost 2A
KERNEL=="axp20x-battery",
ATTR{constant_charge_current_max}="2500000",
ATTR{constant_charge_current}="2400000"