USB: serial: sierra: put reset_resume callback back.

A few patches ago, I removed the reset_resume callback in this driver.
Now that the usb-serial core supports reset_resume, put this driver
callback back as well, so it should work identically to how it was
originally.

Now if this function really is doing what it should be doing, well,
that's a different story, but we are at least doing the identical thing
that we were before...

Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Johan Hovold <jhovold@gmail.com>
Cc: Anton Samokhvalov <pg83@yandex.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/sierra.c

@@ -1039,9 +1039,16 @@ static int sierra_resume(struct usb_serial *serial)
 	return ec ? -EIO : 0;
 }
 
+static int sierra_reset_resume(struct usb_serial *serial)
+{
+	dev_err(&serial->dev->dev, "%s\n", __func__);
+	return usb_serial_resume(serial->interface);
+}
+
 #else
 #define sierra_suspend NULL
 #define sierra_resume NULL
+#define sierra_reset_resume NULL
 #endif
 
 static struct usb_serial_driver sierra_device = {
@@ -1065,6 +1072,7 @@ static struct usb_serial_driver sierra_device = {
 	.release           = sierra_release,
 	.suspend	   = sierra_suspend,
 	.resume		   = sierra_resume,
+	.reset_resume	   = sierra_reset_resume,
 	.read_int_callback = sierra_instat_callback,
 };