cs89x0 : packet reception not working

The RxCFG register of the CS89x0 could be configured incorrectly
(because of misplaced parentheses), resulting in the disabling
of packet reception.

Signed-off-by: Jaccon Bastiaansen <jaccon.bastiaansen@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>