[IRDA]: irda-usb, unregister netdev when patch upload fails

In the STIR421x case, when the firmware upload fails, we need to
unregister_netdev. Otherwise we hit a BUG on free_netdev(), if sysfs
is enabled.
 
Signed-off-by: Samuel Ortiz <samuel.ortiz@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>