shipmode: Enable Hi-Z mode using kernel interface

Since kernel 6.3, bq25890 driver allows to enable Hi-Z via sysfs.

default/shipmode/l5-poweroff-shipmode

@@ -24,6 +24,6 @@ fi
 # Only continue setting ship mode when running on battery.
 # Connecting a charger will turn on the phone. The battery will
 # not have been discharged in the meantime though:
-i2cset -f -y 3 0x6a 0x00 0x88
+echo 0 > /sys/class/power_supply/bq25890-charger/online
 # shut off the battery with 10-15 second delay
 i2cset -f -y 3 0x6a 0x09 0x6e