enic: Always use single transmit and single receive hardware queues per device

We believe that our earlier patch for supporting multiple hardware
receive queues per enic device requires more internal testing. At this
point, we think that it's best to disable the use of multiple receive
queues. The current patch provides an effective means for the same.

Also, we continue to disallow multiple hardware transmit queues per
device. But change the way we enforce this in order to maintain
consistency with the way receive queues are handled.

Signed-off-by: Christian Benvenuti <benve@cisco.com>
Signed-off-by: Danny Guo <dannguo@cisco.com>
Signed-off-by: Vasanthy Kolluri <vkolluri@cisco.com>
Signed-off-by: Roopa Prabhu <roprabhu@cisco.com>
Signed-off-by: David Wang <dwang2@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>