ibmvnic: Update XPS assignments during affinity binding

Transmit Packet Steering (XPS) maps cpu numbers to transmit
queues. By running the same connection on the same set of cpu's,
contention for the queue and cache miss rate can be minimized.
When assigning a cpu mask for a tranmit queues irq number, assign
the same cpu mask as the set of cpu's that XPS should use for that
queue.

Signed-off-by: Thomas Falcon <tlfalcon@linux.ibm.com>
Signed-off-by: Dany Madden <drt@linux.ibm.com>
Signed-off-by: Nick Child <nnac123@linux.ibm.com>
Reviewed-by: Rick Lindsley <ricklind@linux.ibm.com>
Reviewed-by: Haren Myneni <haren@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>