netif_set_xps_queue: make cpu mask const

virtio wants to pass in cpumask_of(cpu), make parameter
const to avoid build warnings.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/linux/netdevice.h
Simple merge

diff --cc net/core/dev.c
Simple merge