hwmon: (ina2xx) reinitialize the chip in case it's been reset
Chips from the ina family don't like to be uninitialized. In case the power
is cut-off and restored again the calibration register will be reset
to 0 and both the power and current registers will remain at 0.
Check the calibration register in ina2xx_update_device() and reinitialize
the chip if needed.