ibmvnic: Implement per-queue statistics reporting

Add counters to report number of packets, bytes, and dropped packets for
each transmit queue and number of packets, bytes, and interrupts for each
receive queue. Modify ethtool callbacks to report the new statistics.

Signed-off-by: John Allen <jallen@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>