IB/mlx: Set slid to zero in Ethernet completion struct

IB spec says that a lid should be ignored when link layer is Ethernet,
for example when building or parsing a CM request message (CA17-34).
However, since ib_lid_be16() and ib_lid_cpu16()  validates the slid,
not only when link layer is IB, we set the slid to zero to prevent
false warnings in the kernel log.

Fixes: 62ede777

 ("Add OPA extended LID support")
Reviewed-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>