net-sysfs: store the return of get_netdev_queue_index in an unsigned int

In net-sysfs, get_netdev_queue_index returns an unsigned int. Some of
its callers use an unsigned long to store the returned value. Update the
code to be consistent, this should only be cosmetic.

Signed-off-by: Antoine Tenart <atenart@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>