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" <afd@ti.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201112095715.1993117-3-lee.jones@linaro.orgSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/ina3221.c

@@ -139,7 +139,7 @@ static inline bool ina3221_is_enabled(struct ina3221_data *ina, int channel)
 	       (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