net: Add sysfs value to determine queue traffic class

net: Add sysfs value to determine queue traffic class

Add a sysfs attribute for a Tx queue that allows us to determine the
traffic class for a given queue.  This will allow us to more easily
determine this in the future.  It is needed as XPS will take the traffic
class for a group of queues into account in order to avoid pulling traffic
from one traffic class into another.

Signed-off-by: Alexander Duyck <[email protected]>
Signed-off-by: David S. Miller <[email protected]>