battery_monitor: only run on approved devices
Created by: RobertCNelson
/proc/device-tree/model
TI AM335x BeagleBone Blue TI AM335x BeagleBone Black RoboticsCape TI AM335x BeagleBone Black Wireless RoboticsCape
fixes: https://github.com/StrawsonDesign/Robotics_Cape_Installer/issues/16 Signed-off-by: Robert Nelson robertcnelson@gmail.com