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
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>