hwmon: (ina3221) Demote seemingly unintentional kerneldoc header

This is the only use of kerneldoc in the sourcefile and no
descriptions are provided.

Fixes the following W=1 kernel build warning(s):

drivers/hwmon/ina3221.c:152: warning: Function parameter or member 'ina' not described in 'ina3221_summation_shunt_resistor'

Cc: "Andrew F. Davis" <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>

drivers/hwmon/ina3221.c

···
 	       (ina->reg_config & INA3221_CONFIG_CHx_EN(channel));
 }
 
-/**
+/*
  * Helper function to return the resistor value for current summation.
  *
  * There is a condition to calculate current summation -- all the shunt