usb: common: usb-conn-gpio: Print error on failure to get VBUS

The exact error that happened trying to get the VBUS supply can be
useful to troubleshoot what's going on.
Signed-off-by: NThierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20200806160248.3936771-2-thierry.reding@gmail.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/common/usb-conn-gpio.c

@@ -206,7 +206,7 @@ static int usb_conn_probe(struct platform_device *pdev)
 
 	if (IS_ERR(info->vbus)) {
 		if (PTR_ERR(info->vbus) != -EPROBE_DEFER)
-			dev_err(dev, "failed to get vbus\n");
+			dev_err(dev, "failed to get vbus: %ld\n", PTR_ERR(info->vbus));
 		return PTR_ERR(info->vbus);
 	}