RDMA/cxgb4: Fix RDMA_CM_EVENT_UNREACHABLE error for iWARP

RDMA/cxgb4: Fix RDMA_CM_EVENT_UNREACHABLE error for iWARP

[ Upstream commit c659b405b82ead335bee6eb33f9691bf718e21e8 ]

ip_dev_find() always returns real net_device address, whether traffic is
running on a vlan or real device, if traffic is over vlan, filling
endpoint struture with real ndev and an attempt to send a connect request
will results in RDMA_CM_EVENT_UNREACHABLE error.  This patch fixes the
issue by using vlan_dev_real_dev().

Fixes: 830662f6f032 ("RDMA/cxgb4: Add support for active and passive open connection with IPv6 address")
Link: https://patch.msgid.link/r/20241007132311.70593-1-anumula@chelsio.com
Signed-off-by: Anumula Murali Mohan Reddy <anumula@chelsio.com>
Signed-off-by: Potnuri Bharat Teja <bharat@chelsio.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>