drivers: net: xgene: fix extra IRQ issue

For interrupt controller that doesn't support irq_disable and hardware
with level interrupt, an extra interrupt may be pending. This patch fixes
the issue by setting IRQ_DISABLE_UNLAZY flag for the interrupt line,
as suggested by,

'commit e9849777 ("genirq: Add flag to force mask in
		       disable_irq[_nosync]()")'

Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Tested-by: Toan Le <toanle@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>