usb: phy: twl6030-usb: check regulator_enable return value

Since regulator_enable() is going to be marked as __must_check in the
next merge window, always check regulator_enable() return value and
print a warning if it fails.

Cc: Hema HK <hemahk@ti.com>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/phy/phy-twl6030-usb.c

@@ -211,6 +211,7 @@ static irqreturn_t twl6030_usb_irq(int irq, void *_twl)
 	struct twl6030_usb *twl = _twl;
 	enum omap_musb_vbus_id_status status = OMAP_MUSB_UNKNOWN;
 	u8 vbus_state, hw_state;
+	int ret;
 
 	hw_state = twl6030_readb(twl, TWL6030_MODULE_ID0, STS_HW_CONDITIONS);
 
@@ -218,7 +219,10 @@ static irqreturn_t twl6030_usb_irq(int irq, void *_twl)
 						CONTROLLER_STAT1);
 	if (!(hw_state & STS_USB_ID)) {
 		if (vbus_state & VBUS_DET) {
-			regulator_enable(twl->usb3v3);
+			ret = regulator_enable(twl->usb3v3);
+			if (ret)
+				dev_err(twl->dev, "Failed to enable usb3v3\n");
+
 			twl->asleep = 1;
 			status = OMAP_MUSB_VBUS_VALID;
 			twl->linkstat = status;
@@ -245,12 +249,15 @@ static irqreturn_t twl6030_usbotg_irq(int irq, void *_twl)
 	struct twl6030_usb *twl = _twl;
 	enum omap_musb_vbus_id_status status = OMAP_MUSB_UNKNOWN;
 	u8 hw_state;
+	int ret;
 
 	hw_state = twl6030_readb(twl, TWL6030_MODULE_ID0, STS_HW_CONDITIONS);
 
 	if (hw_state & STS_USB_ID) {
+		ret = regulator_enable(twl->usb3v3);
+		if (ret)
+			dev_err(twl->dev, "Failed to enable usb3v3\n");
 
-		regulator_enable(twl->usb3v3);
 		twl->asleep = 1;
 		twl6030_writeb(twl, TWL_MODULE_USB, 0x1, USB_ID_INT_EN_HI_CLR);
 		twl6030_writeb(twl, TWL_MODULE_USB, 0x10, USB_ID_INT_EN_HI_SET);