mfd: ab8500-gpadc: Add CONFIG_PM_RUNTIME to runtime_suspend/runtime_resume

Add CONFIG_PM_RUNTIME to runtime_suspend/runtime_resume functions
to fix the build warnings when CONFIG_PM_RUNTIME is not selected.
This is because runtime PM callbacks defined by SET_RUNTIME_PM_OPS
are only used when the CONFIG_PM_RUNTIME is enabled.

drivers/mfd/ab8500-gpadc.c:870:12: warning: 'ab8500_gpadc_runtime_suspend' defined but not used [-Wunused-function]
drivers/mfd/ab8500-gpadc.c:878:12: warning: 'ab8500_gpadc_runtime_resume' defined but not used [-Wunused-function]
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/ab8500-gpadc.c

@@ -867,6 +867,7 @@ static void ab8500_gpadc_read_calibration_data(struct ab8500_gpadc *gpadc)
 		gpadc->cal_data[ADC_INPUT_VBAT].offset);
 }
 
+#ifdef CONFIG_PM_RUNTIME
 static int ab8500_gpadc_runtime_suspend(struct device *dev)
 {
 	struct ab8500_gpadc *gpadc = dev_get_drvdata(dev);
@@ -885,6 +886,7 @@ static int ab8500_gpadc_runtime_resume(struct device *dev)
 		dev_err(dev, "Failed to enable vtvout LDO: %d\n", ret);
 	return ret;
 }
+#endif
 
 static int ab8500_gpadc_suspend(struct device *dev)
 {