net: bcmgenet: use __napi_schedule_irqoff()

bcmgenet_isr1() and bcmgenet_isr0() run in hard irq context,
we do not need to block irq again.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Petri Gynther <pgynther@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>