UPSTREAM: HID: input: map battery system charging

HID descriptors with Battery System (0x85) Charging (0x44) usage are
ignored and POWER_SUPPLY_STATUS_DISCHARGING is always reported to user
space, even when the device is charging.

Map this usage and when it is reported set the right charging status.

In addition, add KUnit tests to make sure that the charging status is
correctly set and reported. They can be run with the usual command:

    $ ./tools/testing/kunit/kunit.py run --kunitconfig=drivers/hid

Change-Id: Ib42e823c5fccfe0c281d8855e124c03b20978132
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
(cherry picked from commit a608dc1c)
Bug: 305125317
Cc: Lu Guohong <luguohong@xiaomi.corp-partner.google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>