power: supply: qti_battery_charger: Enable Ship mode shutdown

This feature is to enable the disconnection of the battery from the
device as the final step in the assembly of a phone on the factory floor
to prevent battery rundown while in transit to the hands of the final
consumer.

Usage:
  # echo 1 > /sys/class/qcom-battery/ship_mode_en
  Following this, either manually shut down using power key, or:
  # reboot -p

Change-Id: Ifef053c6ebb3b86c10f9dbe3c9c47d7c3548d95b
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>