hv_netvsc: use napi_schedule_irqoff

[ Upstream commit 68633edaef655ce94e51088ecef5dd4e1d2f6f34 ]

Since the netvsc_channel_cb is already called in interrupt
context from vmbus, there is no need to do irqsave/restore.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>