hwmon: (ina238) Constify struct regmap_config

`ina238_regmap_config` is not modified and can be declared as const to
move its data to a read-only section.

Signed-off-by: Javier Carrasco <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>

drivers/hwmon/ina238.c

···
 #define INA238_BUS_VOLTAGE_LSB		3125 /* 3.125 mV/lsb */
 #define INA238_DIE_TEMP_LSB		125 /* 125 mC/lsb */
 
-static struct regmap_config ina238_regmap_config = {
+static const struct regmap_config ina238_regmap_config = {
 	.max_register = INA238_REGISTERS,
 	.reg_bits = 8,
 	.val_bits = 16,