mfd: ab8500-gpadc: Complain if we fail to enable vtvout LDO

Since commit c8801a8e
"regulator: core: Mark all get and enable calls as __must_check",
we must check return value of regulator_enable() to silence below build warning.

CC drivers/mfd/ab8500-gpadc.o
drivers/mfd/ab8500-gpadc.c: In function 'ab8500_gpadc_runtime_resume':
drivers/mfd/ab8500-gpadc.c:598:18: warning: ignoring return value of 'regulator_enable', declared with attribute warn_unused_result [-Wunused-result]
drivers/mfd/ab8500-gpadc.c: In function 'ab8500_gpadc_probe':
drivers/mfd/ab8500-gpadc.c:655:18: warning: ignoring return value of 'regulator_enable', declared with attribute warn_unused_result [-Wunused-result]

Also convert to devm_regulator_get(), this fixes a missing regulator_put() call
in ab8500_gpadc_remove().

Signed-off-by: Axel Lin <[e-mail]>
Signed-off-by: Samuel Ortiz <[e-mail]>

drivers/mfd/ab8500-gpadc.c

···
 static int ab8500_gpadc_runtime_resume(struct device *dev)
 {
 	struct ab8500_gpadc *gpadc = dev_get_drvdata(dev);
+	int ret;
 
-	regulator_enable(gpadc->regu);
-	return 0;
+	ret = regulator_enable(gpadc->regu);
+	if (ret)
+		dev_err(dev, "Failed to enable vtvout LDO: %d\n", ret);
+	return ret;
 }
 
 static int ab8500_gpadc_runtime_idle(struct device *dev)
···
 	}
 
 	/* VTVout LDO used to power up ab8500-GPADC */
-	gpadc->regu = regulator_get(&pdev->dev, "vddadc");
+	gpadc->regu = devm_regulator_get(&pdev->dev, "vddadc");
 	if (IS_ERR(gpadc->regu)) {
 		ret = PTR_ERR(gpadc->regu);
 		dev_err(gpadc->dev, "failed to get vtvout LDO\n");
···
 
 	platform_set_drvdata(pdev, gpadc);
 
-	regulator_enable(gpadc->regu);
+	ret = regulator_enable(gpadc->regu);
+	if (ret) {
+		dev_err(gpadc->dev, "Failed to enable vtvout LDO: %d\n", ret);
+		goto fail_enable;
+	}
 
 	pm_runtime_set_autosuspend_delay(gpadc->dev, GPADC_AUDOSUSPEND_DELAY);
 	pm_runtime_use_autosuspend(gpadc->dev);
···
 	list_add_tail(&gpadc->node, &ab8500_gpadc_list);
 	dev_dbg(gpadc->dev, "probe success\n");
 	return 0;
+
+fail_enable:
 fail_irq:
 	free_irq(gpadc->irq, gpadc);
 fail: