net: thunderx: Use napi_schedule_irqoff()

napi_schedule is being called from hard irq context, hence
switch to napi_schedule_irqoff which avoids unneeded call
to local_irq_save and local_irq_restore.

Signed-off-by: Sunil Goutham <sgoutham@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>