staging:r8188eu: Remove rx_handler_data unnecessary read

Rx handler (assigned with netdev_rx_handler_register,
called from __netif_receive_skb()) uses value of dev->rx_handler_data.
The driver has no rx handler and does not need it, so remove rx_handler_data read.

Signed-off-by: Ivan Safonov <insafonov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>