cdc-wdm: return correct error codes

Lieing to user space is wrong. The real reason for a failure
to write should be returned to user space.

Signed-off-by: Oliver Neukum <[e-mail]>0
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/class/cdc-wdm.c

···
 	desc->werr = 0;
 	spin_unlock_irq(&desc->iuspin);
 	if (we < 0)
-		return -EIO;
+		return usb_translate_errors(we);
 
 	buf = kmalloc(count, GFP_KERNEL);
 	if (!buf) {