staging: r8188eu: remove unnecessary type cast of rtw_netdev_priv() result

The type cast
padapter = (struct adapter *)rtw_netdev_priv(dev);
do nothing because type of rtw_netdev_priv() result
is (struct adapter *).

Signed-off-by: Ivan Safonov <insafonov@gmail.com>
Link: https://lore.kernel.org/r/20200815203306.121039-1-insafonov@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>