SMBus smart battery driver

This adds support for reading the voltage of a "smart battery" using I2C which is mostly compatible with SMBus.
Is the orb declare here required? It seems to be already correctly present here:
https://github.com/PX4/Firmware/blob/1fdc666bb0be393f048c85b1827494beedff0426/src/modules/uORB/topics/battery_status.h#L67