RDMA/cma: Set IBoE SL (user-priority) by egress map when using vlans

On top of commit 366cddb4 "IB/rdma_cm: TOS <=> UP mapping for IBoE", add
support for case vlan egress map is used.

When the IBoE session is being set over a vlan, inherit the socket priority
to vlan priority mapping which was configured for the vlan device egress map.

Signed-off-by: Eyal Perry <eyalpe@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>