hwmon: (dell-smm) Mark i8k_get_fan_nominal_speed as __init

Mark function i8k_get_fan_nominal_speed() as __init since
it is only used in code also marked as __init.
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Reviewed-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20210814143637.11922-5-W_Armin@gmx.deSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/dell-smm-hwmon.c

@@ -309,7 +309,7 @@ static int i8k_get_fan_type(struct dell_smm_data *data, int fan)
 /*
  * Read the fan nominal rpm for specific fan speed.
  */
-static int i8k_get_fan_nominal_speed(const struct dell_smm_data *data, int fan, int speed)
+static int __init i8k_get_fan_nominal_speed(const struct dell_smm_data *data, int fan, int speed)
 {
 	struct smm_regs regs = { .eax = I8K_SMM_GET_NOM_SPEED, };