cxgb4: get naming correct for iscsi queues

All the upper level protocols like rdma, iscsi have their own offload rx
queues, so instead of using the generic naming convention be specific
while naming them. Improves code readability

Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>