hwmon: (ina3221) Use _info API to register hwmon device
The hwmon core has a newer API which abstracts most of common
things in the core so as to simplify the hwmon device drivers.
This patch implements this _info API to ina3221 hwmon driver.
It also reduces the binary size:
text data bss dec hex filename
5114 1712 0 6826 1aaa drivers/hwmon/ina3221_before.o
4456 440 0 4896 1320 drivers/hwmon/ina3221.o