ibmvnic: Record SKB RX queue during poll

Map each RX SKB to the RX queue associated with the driver's RX SCRQ.
This should improve the RX CPU load balancing issues seen by the
performance team.

Signed-off-by: Thomas Falcon <tlfalcon@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>