mfd: max14577: max14577_{suspend,resume}() should depend on CONFIG_PM_SLEEP

If CONFIG_PM_SLEEP=n:

drivers/mfd/max14577.c:177: warning: ‘max14577_suspend’ defined but not used
drivers/mfd/max14577.c:200: warning: ‘max14577_resume’ defined but not used
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/max14577.c

@@ -173,6 +173,7 @@ static const struct i2c_device_id max14577_i2c_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, max14577_i2c_id);
 
+#ifdef CONFIG_PM_SLEEP
 static int max14577_suspend(struct device *dev)
 {
 	struct i2c_client *i2c = container_of(dev, struct i2c_client, dev);
@@ -208,6 +209,7 @@ static int max14577_resume(struct device *dev)
 
 	return 0;
 }
+#endif /* CONFIG_PM_SLEEP */
 
 static struct of_device_id max14577_dt_match[] = {
 	{ .compatible = "maxim,max14577", },