mmc: dw_mmc: Check return value of regulator_enable

regulator_enable() is declared with __must_check attribute.
Hence check the return value to ensure that the regulator is enabled.

Fixes the following warning:

drivers/mmc/host/dw_mmc.c:2461:19: warning:
ignoring return value of ‘regulator_enable’, declared with attribute
warn_unused_result [-Wunused-result]
drivers/mmc/host/dw_mmc.c: In function ‘dw_mci_init_slot’:
drivers/mmc/host/dw_mmc.c:1994:19: warning:
ignoring return value of ‘regulator_enable’, declared with attribute
warn_unused_result [-Wunused-result]
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Acked-by: Seungwon Jeon <tgih.jun@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/dw_mmc.c

@@ -1997,8 +1997,14 @@ static int dw_mci_init_slot(struct dw_mci *host, unsigned int id)
 	if (IS_ERR(host->vmmc)) {
 		pr_info("%s: no vmmc regulator found\n", mmc_hostname(mmc));
 		host->vmmc = NULL;
-	} else
-		regulator_enable(host->vmmc);
+	} else {
+		ret = regulator_enable(host->vmmc);
+		if (ret) {
+			dev_err(host->dev,
+				"failed to enable regulator: %d\n", ret);
+			goto err_setup_bus;
+		}
+	}
 
 	if (dw_mci_get_cd(mmc))
 		set_bit(DW_MMC_CARD_PRESENT, &slot->flags);
@@ -2464,8 +2470,14 @@ int dw_mci_resume(struct dw_mci *host)
 {
 	int i, ret;
 
-	if (host->vmmc)
-		regulator_enable(host->vmmc);
+	if (host->vmmc) {
+		ret = regulator_enable(host->vmmc);
+		if (ret) {
+			dev_err(host->dev,
+				"failed to enable regulator: %d\n", ret);
+			return ret;
+		}
+	}
 
 	if (!mci_wait_reset(host->dev, host)) {
 		ret = -ENODEV;