cxgb4: fix Tx multi channel port rate limit

T6 can support 2 egress traffic management channels per port to
double the total number of traffic classes that can be configured.
In this configuration, if the class belongs to the other channel,
then all the queues must be bound again explicitly to the new class,
for the rate limit parameters on the other channel to take effect.

So, always explicitly bind all queues to the port rate limit traffic
class, regardless of the traffic management channel that it belongs
to. Also, only bind queues to port rate limit traffic class, if all
the queues don't already belong to an existing different traffic
class.

Fixes: 4ec4762d

 ("cxgb4: add TC-MATCHALL classifier egress offload")
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>