USB: power availability check for berry_charge

this introduces a sanity check into berry_charge to give up before
damage is done if we lack juice.

Signed-off-by: Oliver Neukum <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/misc/berry_charge.c

···
 {
 	struct usb_device *udev = interface_to_usbdev(intf);
 
+	if (udev->bus_mA < 500) {
+		dbg(&udev->dev, "Not enough power to charge available\n");
+		return -ENODEV;
+	}
+
 	dbg(&udev->dev, "Power is set to %dmA\n",
 	    udev->actconfig->desc.bMaxPower * 2);