ibmvnic: Modify buffer size and number of queues on failover

Using newer backing devices can cause the required padding at the end of
buffer as well as the number of queues to change after a failover.
Since we currently assume that these values never change, after a
failover to a backing device with different capabilities, we can get
errors from the vnic server, attempt to free long term buffers that are
no longer there, or not free long term buffers that should be freed.

This patch resolves the issue by checking whether any of these values
change, and if so perform the necessary re-allocations.

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