misc: keba: Add battery device

Add support for the battery auxiliary device. This enables monitoring of
the battery.

Signed-off-by: Gerhard Engleder <eg@keba.com>
Link: https://lore.kernel.org/r/20241011191257.19702-8-gerhard@engleder-embedded.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>