ibmvnic: Start completion queue negotiation at server-provided optimum values

Use the opt_* fields to determine the starting point for negotiating the
number of tx/rx completion queues with the vnic server. These contain the
number of queues that the vnic server estimates that it will be able to
allocate. While renegotiation may still occur, using the opt_* fields will
reduce the number of times this needs to happen and will prevent driver
probe timeout on systems using large numbers of ibmvnic client devices per
vnic port.

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