cxgb4: reject overlapped queues in TC-MQPRIO offload

A queue can't belong to multiple traffic classes. So, reject
any such configuration that results in overlapped queues for a
traffic class.

Fixes: b1396c2b

 ("cxgb4: parse and configure TC-MQPRIO offload")
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>