KS8695: fix ks8695_rx_irq() bug.

ks8695 rx irq is edge-level. Before arriving at irq handler, the
corresponding status bit has been clear(irq's ack).
So we should not check it after that.

Signed-off-by: zeal <zealcook@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>