iw_cxgb4: use tos when finding ipv6 routes

When IPv6 support was added, the correct tos was not passed to
cxgb_find_route6(). This potentially results in the wrong route entry.

Fixes: 830662f6

 ("RDMA/cxgb4: Add support for active and passive open connection with IPv6 address")
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>