vmxnet3: Use single tx queue when CONFIG_PCI_MSI not defined

Resending this patch with few changes.

Avoid multiple queues when MSI or MSI-X not available

Limit number of Tx queues to 1 if MSI/MSI-X support is not configured in
the kernel. This will make number of tx and rx queues equal when MSI/X
is not configured thus providing better performance.

Signed-off-by: Bhavesh Davda <bhavesh@vmware.com>
Signed-off-by: Shreyas N Bhatewara <sbhatewara@vmware.com>
Signed-off-by: David S. Miller <davem@davemloft.net>